Karyotyp-Phenotyp-Lorrelation bei einem 46,Xdel(X)(p22)-Befund

Summary In a patient with a height of 1.46 m, short neck and cubitus valgus the unbalanced karyotype 46,Xdel(X)(p22) was found. The mother of the proband has the balanced karyotype 46,Xt(X;15)(p22;p1). The mother is 1.56 m tall and has a short neck and cubitus valgus too. For this reason the deletion of the Xp22 band seems to cause the short stature of Turner patients. Our proband has had 2 pregnancies which ended as abortions in the 2nd and 4th month.As Giraud et al. (1974) have shown the deletion of the dark middle bande of the short X chromosome arm induces a slight dysgenesie of the gonade.     

Correlations between individual and familial variables in Turner's syndrome]

In 20 cases of Turner's syndrome (10 with complete X monosomy, 10 with partial X monosomy or mosaicism) aged 3.47 to 15.5 years, the stature of the individual cases and their parents were evaluated. A significant frequency of short stature in mothers (25% below--2.0 S.D.S) has been observed, with a significant difference compared to the mean female stature of the general population. No significant difference has been observed on the stature of fathers. There was a closer correlation with mother's height (r = 0.65, p = 0.001) than with father's height (p = 0.07).     

An abnormal dicentric X chromosome in a patient with short stature and gonadal dysgenesis.

A 16 year-old girl with short stature and gonadal dysgenesis was found to have a chromosomal complement consisting of 46,X,dic(X) (qter yields p22::p22 yields qter). When comparing her clinical features with 7 other cases who appeared to have precisely the same abnormal dicentric X, it was found that even though the percent of 45,X cells present varied considerably from patient to patient, these patients were remarkably similar and the stigmata, of Turner's syndrome were minimal in this group as a whole.     

Short-arm deletion of an X chromosome (45,XO/46,XX p-)

Summary A 31-year-old female patient with short stature, signs of gonadal dysgenesis, and slight Turner signs is described with a mosaic 45,XO/46,XX del (X) (qterp11) determined with trypsin Giemsa-banding and C-staining. BUdR incorporation indicated the deleted X to be late replicating.     

Partial Turner's syndrome in four girls with Xq duplication and Xp deficiency

Summary Four girls with some clinical symptoms of Turner's syndrome had Xq duplication and Xp deficiency, their karyotypes being 46,X,dup(X)(p113;q11), 46,X,dup(X)(p212;q211), 46,X,dup(X)(p225;q13), and 46,X,dup(X)(p222;q213). No mosaicism was found.The major clinical findings, short stature, lack of pterygium colli, and no continuous gamete production, are compared with those in three previously published cases.     

Short arm deletion of an X chromosome, 46,XXp-

Summary A 27-year-old patient of short stature with primary amenorrhea and other slight Turner signs showed a 46,XX,del(X) (qterp11:) karyotype, identified by a combination of fluorescence and giemsa-banding technique. By BUdR incorporation the deleted X chromosome was shown to be the late replicating one.     

Trisomy for the short arm of chromosome No. 10

To the authors knowledge there is a single previous report of confirmed trisomy for the short arm of chromosome No 10 (Hustinx et al., 1974). In this paper we present a further case of trisomy 10p, resulting from 3 : 1 segregation of maternal balanced translocation, t(3;10)(q;11), in a female infant aged 7 months and showing numerous somatic anomalies.     

Duplication of the short arm of the X chromosome in mother and daugther

An 11-year-old girl with short stature, mental retardation, and mild dysmorphic features was found to have an inverted duplication of most of the short arm of the X chromosome [dic inv dup(X)(qterp22.3: :p22.3 cen:)]. Her mother, who is also short and retarded, carries the same duplication. Fluorescence in situ hybridization with an X chromosome library, and with X centromerespecific alpha satellite and telomere probes, was useful in characterizing the duplication. In most females with structurally abnormal X chromosomes, the abnormal chromosome is inactivated. Although the duplicated X was consistently late replicating in the mother, X chromosome inactivation studies in the proband indicated that in 11% of her lymphocytes the duplicated X was active.     

Translocation(X;Y)(p22.33;p11.2) in XX males: Etiology of male phenotype

Summary Analysis of G-banded prometaphase chromosomes from three XX males revealed extra bands on the distal end of one X short arm. These bands were similar both in size and staining properties to the distal Y short arm of their fathers (in the two cases examined) and also to other chromosomally normal males. The extra material on the abnormal X chromosomes was not C-or G-11 positive in the two cases examined, suggesting that the proximal Y long arm was not present.Previous karyotype-phenotype correlations with structurally altered Y chromosomes provided evidence for localization of male determinants on the Y short arm. The present findings in XX males provide support for more precise localization, to bands p11.2pter of Y short arm.     

Center for barr body condensation. A case of Turner's syndrome with 45,X/46,X,dic(X) (Xqter→ p22::p22→qter)

Summary An 11-year-old girl with karyotype 45,X/46,X,dic(X) (Xqterp22::p22qter) is presented. The abnormal X is always found to be the inactive and late replicating X, and according to previous investigations by Therman et al. (1974) part of the cells are seen to have bipartite Barr bodies.     

Atypical Deletion in Williams-Beuren Syndrome Critical Region Detected by MLPA in a Patient with Supravalvular Aortic Stenosis and Learning Difficulty

Williams-Beuren syndrome (WBS) is a genetic disease characterized by distinct facial features,short stature,hypotonia,mental retardation,overfriendly and hyper-social behavior,congenital heart disease,infantile hypercalcemia,arterial hypertension and other variable clinical manifestations in organs and systems such as the kidneys,eyes,gastrointestinal and osteoarticular systems (Morris and Mervis,2000).This mental retardation syndrome occurs in 1/20,000 live births (Meyer-Lindenberg et al.,2006).It is caused by a 1.55-1.84 Mb microdeletion in 7q 11.23,a region containing approximately 28genes.Depending on the genes deleted,the phenotypes of WBS patients range from isolated supravalvular aortic stenosis (SVAS) to full expression of the WBS characteristics.Most cases are sporadic (Ewart et al.,1993;Perez Jurado et al.,1996).     

Aniridia-Wilms' tumor association: evidence for specific deletion of 11p13.

A 7-year-old boy with aniridia, Wilms' tumor, and mental retardation, previously reported as having an interstitial deletion of the short arm of chromosome 8 resulting from a t(8p+;11q-) translocation (Ladda et al., 1974), has been restudied using high-resolution trypsin-Giemsa banding of prometaphase chromsomes. The results revealed a complex rearrangement with four break points in 8p, 11p, and 11q, leading to a net loss of an interstitial segment of 11p (region p1407 yields p1304) but not of 8p. His red blood cells contained normal activities of glutathione reductase (gene on 8p) and lactate dehydrogeanse A (gene on 11p12), indicating a gene dosage consistent with the chromosomal findings. The revised interpretation of this case agrees with seven others reported as having aniridia and interstitial 11p deletions in establishing the distal half of band 11p13 as the site of gene(s) which lead to aniridia and predispose to Wilms' tumor if present in a hemizygous state. Possible relationships between heterozygous deletion of specific chromosomal bands 11p13 and 13q14 and the autosomal dominant disorders aniridia, Wilms' tumor, and retinoblastoma, respectively, are discussed.     

Chondrodysplasia punctata with X;Y translocation

Summary We have studied a family in which the mother and her son were carriers of an X;Y translocation, der(X)t(X;Y) (p22.3;q11). The mother was of slightly short stature and had mildly short upper extremities. The son had epiphyseal punctate calcifications, mildly short extremities, a flattened nasal bridge, and mental retardation (chondrodysplasia punctata). The extra bands on the short arm of the X chromosome were identified as deriving from the long arm of the Y chromosome, using in situ hybridization with a Y-chromosome-specific DNA probe (pHY10). The chondrodysplasia punctata seen in our case may be associated with the abnormality of the distal short arm of the X chromosome caused by X;Y translocation.     

Guilt by association: What p120-catenin has to hide

Members of the p120-catenin family associate with cadherins and regulate their stability at the plasma membrane. How p120-catenin limits cadherin endocytosis has long remained a mystery. In this issue, Nanes et al. (2012. J. Cell Biol. doi:10.1083/jcb.201205029) identify a conserved acidic motif within cadherins that acts as a physical platform for p120-catenin binding. However, in the absence of p120-catenin, the motif acts as an endocytic signal. These results provide new insight into p120-catenin’s role as guardian of intercellular junction dynamics.Adhesion receptors of the classical cadherin family have a major role in establishing tissue organization and maintaining tissue homeostasis (Gumbiner, 1996). Classical cadherins are transmembrane glycoproteins that use their extracellular domains to establish calcium-dependent trans homophilic interactions with cadherins in neighboring cells. To enhance adhesive strength, cadherin ectodomains oligomerize through lateral (cis) interactions, whereas their cytoplasmic domains anchor to the actomyosin cytoskeleton. The cytoplasmic domain of cadherins is highly conserved and binds to proteins called catenins. p120-catenin (p120) associates with the transmembrane adjacent domain (juxtamembrane; JMD) of the cadherin cytoplasmic tail, whereas β-catenin interacts with the more distal portion of cadherin’s cytoplasmic domain. β-Catenin in turn, binds α-catenin, which, through multiple interactions, both indirect and direct, can associate with the actin cytoskeleton (Perez-Moreno and Fuchs, 2006).Cellular rearrangements are orchestrated by dynamic assembly/disassembly of cadherin complexes. The process is fueled by endocytosis of cadherin complexes (Le et al., 1999; de Beco et al., 2009). Endocytosis can be stimulated by proteins that associate with cadherin–catenin complexes, including proteases that shed the cadherin ectodomains, and the ubiquitin ligase Hakai (Fujita et al., 2002). Cadherin internalization can be regulated by different pathways depending on the cellular context, involving clathrin-dependent and clathrin-independent mechanisms. These endocytic processes must be carefully regulated, as an untimely destabilization of cadherin-mediated adhesion can lead to alterations in tissue architecture and growth, features of several diseases, including cancers (Mosesson et al., 2008).In the past decade, p120 catenins (p120, ARVCF, δ-catenin, and p0071) have emerged as critical regulators of cadherin-mediated adhesion (Reynolds, 2007). p120, the founding family member, is a component of cadherin complexes (Reynolds et al., 1994), and its association with the cadherin JMD is important for retaining cadherins at the membrane (Ireton et al., 2002). Moreover, p120 loss causes rapid internalization of cadherins, followed by proteasomal and/or lysosomal-mediated degradation (Davis et al., 2003; Xiao et al., 2003a,b, 2005; Miyashita and Ozawa, 2007).Although these studies expose p120 as a master regulator of cadherin levels at the membrane, exactly how p120 governs cadherin endocytosis rates has remained unclear. Based upon experiments in which endocytic machinery components (clathrin, dynamin, and AP2) have been impaired (Chiasson et al., 2009) or cadherin endocytic motifs have been mutated (Hong et al., 2010; Troyanovsky et al., 2007), researchers have posited that p120 binding to cadherins may in some way prevent junctional complex endocytosis. In this issue, Nanes et al. add new molecular insights into the mechanism. The authors show that the VE-cadherin JMD functions as a bimodal platform for either p120 binding or endocytic signaling. Moreover, they identify a key conserved amino acid residue within the JMD, which, when mutated, blocks endocytosis without the need for p120.Recently, the cocrystallization of p120 bound to E-cadherin’s JMD has yielded insights into the essential residues of this binding interface (Ishiyama et al., 2010). Previous studies had attributed the core function of p120-cadherin to its ability to bind and mask a dileucine endocytic motif present in the JMD (Miyashita and Ozawa, 2007; Hong et al., 2010). The crystal structure showed that interactions between p120 and the JMD domain might be sufficient to sterically prevent accessibility of the dileucine cadherin endocytic motif to endocytic adaptors such as the AP2-clathrin adaptor, thereby placing this motif at the crux of the bimodal switch controlling the mutually exclusive binding of either p120 or the endocytic machinery.The affinity of p120 and AP2 for the JMD dileucine motif is similar, pointing toward the existence of a balanced regulation of cadherin endocytic rates and cadherin retention at the membrane. However, evaluating this balance in cellular contexts has not been possible because of the inability to uncouple p120 binding to the JMD and endocytosis. Nanes et al. (2012) have now overcome this hurdle. They first used a simulated model of the p120–E-cadherin crystal structure, which highlighted a conserved p120-binding region that is present in the JMD of both VE- and E-cadherin. However, the VE-cadherin JMD lacked endocytic dileucine and tyrosine residues present in E-cadherin, which are involved in clathrin internalization and Hakai-dependent ubiquitination, respectively.Because both types of adherens junctions undergo dynamic endocytic-based remodeling, the authors astutely realized that they might be able to exploit VE- and E-cadherin differences to unearth novel endocytic signals within the sequence that might be conserved among cadherins. To this end, the author first used mutant VE-cadherin chimeric proteins, consisting of the cytoplasmic domain of VE-cadherin fused to the extracellular domain of the IL-2 receptor, and internalization assays. They discovered that the core p120-binding region on its own was endocytosed, in a fashion similar to the full VE-cadherin cytoplasmic tail. This occurred in a clathrin-dependent manner, as previously observed in Kowalzcyk’s laboratory (Chiasson et al., 2009). Point mutagenesis identified some mutants no longer able to bind p120, which is consistent with previous findings (Thoreson et al., 2000). But the authors made an interesting finding: mutations in a conserved acidic motif (DEE) within the p120-core binding region of the JMD displayed loss of p120 binding and also blocked cadherin internalization (Fig. 1). Moreover, DEE mutant VE-cadherins localized stably at the membrane even in the absence of p120, although with an increased diffusion within the membrane. This increase in mobility suggests a reduction in cadherin lateral clustering, a process modulated by the binding of p120 to the JMD (Yap et al., 1998). Interestingly, in crystal structures, the E-cadherin JMD binding to p120 induced oligomerization of the complex (Ishiyama et al., 2010).Open in a separate windowFigure 1.Model of VE-cadherin stabilization at the cell membrane. (A) VE-cadherin binds to p120 and β-catenin. p120 associates with the juxtamembrane (JMD) domain of the cadherin cytoplasmic tail, whereas β-catenin binds to the more distal portion (catenin binding domain, CBD). Cadherin internalization is triggered by p120 dissociation, exposing a conserved endocytic factor recognition motif (DEE; 646–648) within the JMD. (B) When this motif is mutated in VE-cadherin, adherens junctions are resistant to endocytosis independent of p120 binding.These new tools now allow uncoupling of p120 binding from cadherin endocytosis, which will be instrumental in unraveling new p120 cadherin roles in cell adhesion. The VE-cadherin mutant that fails to bind to p-120 still coimmunoprecipitates with β-catenin. These findings are intriguing, given that overexpression of p120 can rescue the otherwise poor adhesive properties of cadherins mutant for β-catenin binding (Ohkubo and Ozawa, 1999). In addition, interactions between p120 and α-catenin at adherens junctions seem to contribute in preventing cadherin endocytosis (Troyanovsky et al., 2011). Given these collective results, it will be interesting in the future to measure the binding affinities of endocytosis-uncoupled VE-cadherin mutants for its binding partners.Overall, these data provide strong evidence that the JMD landing pad provides the nuts and bolts of the decision of whether an adherens junction remains at the cell surface or whether it is internalized. But who makes the decision? Recent results from Gumbiner’s group provide a possible clue. They show that cadherin activation stimulates the dephosphorylation of specific Ser/Thr residues within the N-terminal domain of p120, and this in turn stabilizes intercellular adhesion (Petrova et al., 2012).The new tools developed by Kowalczyk’s group (Nanes et al., 2012) will pave the way for researchers to dig further into the mechanism. In the current study, the authors use their newfound tools to analyze the consequences to cell migration when p120-JMD binding is uncoupled from endocytosis. In scratched monolayers of endothelial cells, cell migration was decreased. Importantly, when they examined the VE-cadherin mutant in which p120 binding was blocked but cadherin internalization could proceed normally, cell migration was largely normal. These findings indicate that the migration defects seen in the cells expressing the E-cadherin mutant are rooted in inhibition of endocytosis, rather than lack of p120 recruitment to junctions. They further suggest that endocytic trafficking of cadherins is necessary to transiently destabilize cell–cell contacts that otherwise impede migration. This notion is particularly intriguing given that when E-cadherins are stabilized at intercellular junctions, they can sequester proteins that are required for integrin-based migration (Livshits et al., 2012). Kowalczyk’s findings (Nanes et al., 2012) now suggest a means by which dynamic changes in intercellular adhesion can be achieved to trigger such downstream events.Although less well characterized, there are other regulatory circuits that might also be affected by transiently liberating p120 from intercellular junctions. Thus, for example, p120 enhances cadherin stability through its ability to interact with afadin and Rap1, thereby bridging connections with nectin intercellular junctions (Hoshino et al., 2005). Other direct and indirect p120 associates that might affect cadherin internalization include the endocytic adaptor Numb (Sato et al., 2011) and the signaling enzyme γ-secretase (Kiss et al., 2008). Additionally, p120 can also regulate Rac1 activity, which influences cadherin endocytosis in a clathrin-independent way (Akhtar and Hotchin, 2001). Thus, removing p120 or devising additional mutations to uncouple these interactions may be needed to fully unravel all the mysteries underlying p120’s power in governing intercellular adhesion in tissue development and maintenance (Davis and Reynolds, 2006; Elia et al., 2006; Perez-Moreno et al., 2006; Smalley-Freed et al., 2010; Marciano et al., 2011; Stairs et al., 2011; Chacon-Heszele et al., 2012; Kurley et al., 2012). That said, by dissecting p120’s web at the crossroads between intercellular junction stabilization and endocytosis, Kowalczyk and coworkers (Nanes et al., 2012) now illustrate the power of their approach and provide new insights into how similar strategies might ultimately enable this molecular crossword puzzle to be solved.     

Cell Wall-Degrading Enzymes Enlarge the Pore Size of Intervessel Pit Membranes in Healthy and Xylella fastidiosa-Infected Grapevines

The pit membrane (PM) is a primary cell wall barrier that separates adjacent xylem water conduits, limiting the spread of xylem-localized pathogens and air embolisms from one conduit to the next. This paper provides a characterization of the size of the pores in the PMs of grapevine (Vitis vinifera). The PM porosity (PMP) of stems infected with the bacterium Xylella fastidiosa was compared with the PMP of healthy stems. Stems were infused with pressurized water and flow rates were determined; gold particles of known size were introduced with the water to assist in determining the size of PM pores. The effect of introducing trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA), oligogalacturonides, and polygalacturonic acid into stems on water flux via the xylem was also measured. The possibility that cell wall-degrading enzymes could alter the pore sizes, thus facilitating the ability of X. fastidiosa to cross the PMs, was tested. Two cell wall-degrading enzymes likely to be produced by X. fastidiosa (polygalactuoronase and endo-1,4- β -glucanase) were infused into stems, and particle passage tests were performed to check for changes in PMP. Scanning electron microscopy of control and enzyme-infused stem segments revealed that the combination of enzymes opened holes in PMs, probably explaining enzyme impacts on PMP and how a small X. fastidiosa population, introduced into grapevines by insect vectors, can multiply and spread throughout the vine and cause Pierce''s disease.In grapevine (Vitis vinifera) stems, water moves with the transpiration stream from one vessel to the next, traversing the scalariform bordered pits in the secondary wall (Mullins et al., 1992; Stevenson et al., 2004b). Water must also pass through the pit membrane (PM) that occurs between a pit pair (i.e. opposing pits in adjacent vessels; Mauseth, 1988; Dickison, 2000). A PM is the shared primary cell walls and middle lamella of vessels that were not covered with the secondary wall of neighboring vessel elements as the development of the water conducting system progressed. PMs are composed of cellulose microfibrils embedded in a polysaccharide matrix of hemicellulose and pectins (Mauseth, 1988; Fisher, 2000; Tyree and Zimmermann, 2002). The fine mesh-like polysaccharide structure of PMs provides minute openings (pores) through which water can move with minimal restriction to other vessels or neighboring parenchyma cells. In angiosperm trees, the diameters of most of these pores have been described to vary between 5 and 20 nm (Choat et al., 2003, 2004), but pores of up to several hundred nanometers have occasionally been observed (Sperry et al., 1991; Sano, 2005; Wheeler et al., 2005). The small size of the PM pores is a safety mechanism that limits the expansion of gas bubbles from one cavitated vessel to its neighbors and the movement of pathogens from one infected, water-filled vessel to its neighbors as water moves through the xylem system (Sperry and Tyree, 1988; Nakaho et al., 2000; Tyree and Zimmermann, 2002). It is thought that pore size is largely controlled by the physical arrangement of hydrated pectins and the cross-links that they establish with themselves and other polysaccharides in the PM (Fleischer et al., 1999; Zwieniecki et al., 2001). The infiltration of vessels with solutions having modifications in ion content or pH causes changes in hydraulic resistance that are consistent with swelling or shrinking of pectins and the consequent changes in PM pore size (Zwieniecki et al., 2001).The xylem-limited bacterium Xylella fastidiosa is the causal agent of Pierce''s disease (PD) of grapevines. X. fastidiosa is vectored by sharpshooter (Cicadellidae) and spittlebug (Cercopidae) insects that feed on xylem sap and introduce the bacteria into xylem vessels (Varela et al., 2001). In order for the bacterial population to become systemic, individual bacterial cells must cross the PMs that separate two adjoining vessels. X. fastidiosa is a rod-shaped bacterium with dimensions ranging from 250 to 500 × 1,000 to 4,000 nm (Mollenhauer and Hopkins, 1974), making them too large to pass freely through the majority of the PM pores that have been described in angiosperms. Nevertheless, evidence of X. fastidiosa cells traversing PMs and gaining access to an adjacent vessel has been reported (Newman et al., 2003). This intervessel movement of X. fastidiosa cells was observed too frequently by Newman et al. (2003) to be considered the result of random encounters with damaged PMs; thus, they proposed that X. fastidiosa is able to degrade the grapevine PM. The involvement of cell wall-degrading enzymes during PD first had been proposed based on indirect evidence from the development of internal symptoms and the location of bacteria in X. fastidiosa-infected shoots, but the absence of evidence for bacterial enzyme production limited wide acceptance of this idea (Hopkins, 1989; Fry and Milholland, 1990a; Purcell and Hopkins, 1996). However, the observation of intervessel X. fastidiosa movement described above and reports that the X. fastidiosa genome contains several genes similar to those encoding cell wall-degrading polygalacturonase (PG) and endo-1,4- β -glucanase (EGase) in other bacteria (Simpson et al., 2000; Wulff et al., 2003) suggested the contrary. Indeed, a X. fastidiosa mutant disrupted in the pglA gene, which encodes an endo-PG, was restricted to the point of inoculation and unable to move systemically in grapevine, indicating that PG plays a major role in vessel-to-vessel movement (Roper et al., 2007). Furthermore, recombinant X. fastidiosa PG (Roper et al., 2007) and EGase (this study) are capable of digesting polygalacturonic acid (PGA) and β -1,4 linked glucans, respectively. The recent detection of PG in the xylem sap of infected vines and less severe symptom development in transgenic grapevines expressing a pear (Pyrus communis) PG-inhibiting protein (pear PGIP [pPGIP]) also suggests that X. fastidiosa uses cell wall-degrading enzymes to open up PM pores to facilitate vessel-to-vessel movement (Agüero et al., 2005).We have reported that during early stages of X. fastidiosa infection, some stems presented exceptionally high hydraulic conductivities (higher than comparable healthy stems), which was attributed to enzymatic digestion of the PMs (Perez-Donoso et al., 2007). In this study, the size of PM pores in healthy and X. fastidiosa-infected stems was approximated by flushing the xylem of grapevine stem explants from the base with water containing particles of known size and determining if the particles could be recovered in the water collected from the distal ends of the explants. We also tested the ability of the PG and EGase activities that have been reported in X. fastidiosa (Roper, 2006; Roper et al., 2007) for digesting the intervessel PM and increasing the size of the PM pores and report that the pPGIP inhibits X. fastidiosa’s PG, presumably explaining why expression of the pPGIP-encoding gene in transgenic grapevines suppresses PD development (Agüero et al., 2005). Finally, the effects of stem infiltration with the chelator trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA), PGA (a model homogalacturonan pectin), or oligogalacturonides (OGAs; potential signal molecules generated when PGA is digested by PG) on PM pore size were also evaluated.     

ORM Expression Alters Sphingolipid Homeostasis and Differentially Affects Ceramide Synthase Activity

Sphingolipid synthesis is tightly regulated in eukaryotes. This regulation in plants ensures sufficient sphingolipids to support growth while limiting the accumulation of sphingolipid metabolites that induce programmed cell death. Serine palmitoyltransferase (SPT) catalyzes the first step in sphingolipid biosynthesis and is considered the primary sphingolipid homeostatic regulatory point. In this report, Arabidopsis (Arabidopsis thaliana) putative SPT regulatory proteins, orosomucoid-like proteins AtORM1 and AtORM2, were found to interact physically with Arabidopsis SPT and to suppress SPT activity when coexpressed with Arabidopsis SPT subunits long-chain base1 (LCB1) and LCB2 and the small subunit of SPT in a yeast (Saccharomyces cerevisiae) SPT-deficient mutant. Consistent with a role in SPT suppression, AtORM1 and AtORM2 overexpression lines displayed increased resistance to the programmed cell death-inducing mycotoxin fumonisin B₁, with an accompanying reduced accumulation of LCBs and C16 fatty acid-containing ceramides relative to wild-type plants. Conversely, RNA interference (RNAi) suppression lines of AtORM1 and AtORM2 displayed increased sensitivity to fumonisin B₁ and an accompanying strong increase in LCBs and C16 fatty acid-containing ceramides relative to wild-type plants. Overexpression lines also were found to have reduced activity of the class I ceramide synthase that uses C16 fatty acid acyl-coenzyme A and dihydroxy LCB substrates but increased activity of class II ceramide synthases that use very-long-chain fatty acyl-coenzyme A and trihydroxy LCB substrates. RNAi suppression lines, in contrast, displayed increased class I ceramide synthase activity but reduced class II ceramide synthase activity. These findings indicate that ORM mediation of SPT activity differentially regulates functionally distinct ceramide synthase activities as part of a broader sphingolipid homeostatic regulatory network.Sphingolipids play critical roles in plant growth and development as essential components of endomembranes, including the plasma membrane, where they constitute more than 40% of the total lipid (Sperling et al., 2005; Cacas et al., 2016). Sphingolipids also are highly enriched in detergent-insoluble membrane fractions of the plasma membrane that form microdomains for proteins with important cell surface activities, including cell wall biosynthesis and hormone transport (Cacas et al., 2012, 2016; Perraki et al., 2012; Bayer et al., 2014). In addition, sphingolipids, particularly those with very-long-chain fatty acids (VLCFAs), are integrally associated with Golgi-mediated protein trafficking that underlies processes related to the growth of plant cells (Bach et al., 2008, 2011; Markham et al., 2011; Melser et al., 2011). Furthermore, sphingolipids function through their bioactive long-chain base (LCB) and ceramide metabolites to initiate programmed cell death (PCD), important for mediating plant pathogen resistance through the hypersensitive response (Greenberg et al., 2000; Liang et al., 2003; Shi et al., 2007; Bi et al., 2014; Simanshu et al., 2014).Sphingolipid biosynthesis is highly regulated in all eukaryotes. In plants, the maintenance of sphingolipid homeostasis is vital to ensure sufficient sphingolipids for growth (Chen et al., 2006; Kimberlin et al., 2013) while restricting the accumulation of PCD-inducing ceramides and LCBs until required for processes such as the pathogen-triggered hypersensitive response. Serine palmitoyltransferase (SPT), which catalyzes the first step in LCB synthesis, is generally believed to be the primary control point for sphingolipid homeostasis (Hanada, 2003). SPT synthesizes LCBs, unique components of sphingolipids, by catalyzing a pyridoxal phosphate-dependent condensation of Ser and palmitoyl (16:0)-CoA in plants (Markham et al., 2013). Similar to other eukaryotes, the Arabidopsis (Arabidopsis thaliana) SPT is a heterodimer consisting of LCB1 and LCB2 subunits (Chen et al., 2006; Dietrich et al., 2008; Teng et al., 2008). Research to date has shown that SPT is regulated primarily by posttranslational mechanisms involving physical interactions with noncatalytic, membrane-associated proteins that confer positive and negative regulation of SPT activity (Han et al., 2009, 2010; Breslow et al., 2010). These proteins include a 56-amino acid small subunit of SPT (ssSPT) in Arabidopsis, which was recently shown to stimulate SPT activity and to be essential for generating sufficient amounts of sphingolipids for pollen and sporophytic cell viability (Kimberlin et al., 2013).Evidence from yeast and mammalian research points to a more critical role for proteins termed ORMs (for orosomucoid-like proteins) in sphingolipid homeostatic regulation (Breslow et al., 2010; Han et al., 2010). The Saccharomyces cerevisiae Orm1p and Orm2p negatively regulate SPT through reversible phosphorylation of these polypeptides in response to intracellular sphingolipid levels (Breslow et al., 2010; Han et al., 2010; Roelants et al., 2011; Gururaj et al., 2013; Muir et al., 2014). Phosphorylation/dephosphorylation of ORMs in S. cerevisiae presumably affects the higher order assembly of SPT to mediate flux through this enzyme for LCB synthesis (Breslow, 2013). In this sphingolipid homeostatic regulatory mechanism, the S. cerevisiae Orm1p and Orm2p are phosphorylated at their N termini by Ypk1, a TORC2-dependent protein kinase (Han et al., 2010; Roelants et al., 2011). The absence of this phosphorylation domain in mammalian and plant ORM homologs brings into question the nature of SPT reversible regulation by ORMs in other eukaryotic systems (Hjelmqvist et al., 2002).Sphingolipid synthesis also is mediated by the N-acylation of LCBs by ceramide synthases to form ceramides, the hydrophobic backbone of the major plant glycosphingolipids, glucosylceramide (GlcCer) and glycosyl inositolphosphoceramide (GIPC). Two functionally distinct classes of ceramide synthases occur in Arabidopsis, designated class I and class II (Chen et al., 2008). Class I ceramide synthase activity resulting from the Longevity Assurance Gene One Homolog2 (LOH2)-encoded ceramide synthase acylates, almost exclusively, LCBs containing two hydroxyl groups (dihydroxy LCBs) with 16:0-CoA to form C16 ceramides, which are used primarily for GlcCer synthesis (Markham et al., 2011; Ternes et al., 2011; Luttgeharm et al., 2016). Class II ceramide synthase activities resulting from the LOH1- and LOH3-encoded ceramide synthases are most active in the acylation of LCBs containing three hydroxyl groups (trihydroxy LCBs) with VLCFA-CoAs, including primarily C₂₄ and C₂₆ acyl-CoAs (Markham et al., 2011; Ternes et al., 2011; Luttgeharm et al., 2016). Class II (LOH1 and LOH3) ceramide synthase activity is essential for producing VLCFA-containing glycosphingolipids to support the growth of plant cells, whereas class I (LOH2) ceramide synthase activity is nonessential under normal growth conditions (Markham et al., 2011; Luttgeharm et al., 2015b). It was speculated recently that LOH2 ceramide synthase functions, in part, as a safety valve to acylate excess LCBs for glycosylation, resulting in a less cytotoxic form (Luttgeharm et al., 2015b; Msanne et al., 2015). Recent studies have shown that the Lag1/Lac1 components of the S. cerevisiae ceramide synthase are phosphorylated by Ypk1, and this phosphorylation stimulates ceramide synthase activity in response to heat and reduced intracellular sphingolipid levels (Muir et al., 2014). This finding points to possible coordinated regulation of ORM-mediated SPT and ceramide synthase activities to regulate sphingolipid homeostasis, which is likely more complicated in plants and mammals due to the occurrence of functionally distinct ceramide synthases in these systems (Stiban et al., 2010; Markham et al., 2011; Ternes et al., 2011; Luttgeharm et al., 2016).RNA interference (RNAi) suppression of ORM genes in rice (Oryza sativa) has been shown to affect pollen viability (Chueasiri et al., 2014), but no mechanistic characterization of ORM proteins in plants has yet to be reported. Here, we describe two Arabidopsis ORMs, AtORM1 and AtORM2, that suppress SPT activity through direct interaction with the LCB1/LCB2 heterodimer. We also show that strong up-regulation of AtORM expression impairs growth. In addition, up- or down-regulation of ORMs is shown to differentially affect the sensitivity of Arabidopsis to the PCD-inducing mycotoxin fumonisin B₁ (FB₁), a ceramide synthase inhibitor, and to differentially affect the activities of class I and II ceramide synthases as a possible additional mechanism for regulating sphingolipid homeostasis.     

131例原发性闭经女性的细胞遗传学分析(含世界首报异常核型3例)

原发性闭经是一种原因复杂的疾病, 染色体异常则是发病的主要原因。通过对131例原发性闭经患者的外周血淋巴细胞染色体的G带核型分析, 发现其中83例为正常女性核型, 占63.36%; 各种异常核型48例,占36.64%, 其中包括3例世界首次报道的异常核型[46,X,t(X;1)(q22;p34); 46,X,t(X;5;6)(p11.2;q35;q16); 46,XX,t(4; 9)(q21;p22),t(6;10)(p25;q25),t(11;14)(q23;q32)]。另外, 将33例Turner’s综合征患者的主要异常体征及核型分布分别与Elsheikh等的报道进行比较, 发现矮身材、蹼颈、后发迹低和肘外翻的发生率与文献资料存在显著差异, 说明东西方Turner’s综合征患者临床体征的表现可能存在差异。通过对2例X-常染色体易位携带者的分析, 认为Xp11.2和Xq22区域可能与原发性闭经有关。     

Partial trisomy for the short arm of chromosome 2 due to familial balanced translocation

Summary A partial trisomy for the short arm of chromosome 2 (p21pter) was observed in a severely retarded infant with facial, skeletal, genital, renal, and CNS anomalies. The phenotypically normal mother and older brother had a balanced translocation between the short arm of chromosome 2 and the long arm of chromosome 14: 46,XX-XY,t(2;14)(p21;q32).     

Partial duplication of 17p

Summary An inherited partial duplication syndrome of 17p is described. A comparison of the symptoms of a de novo partial duplication of 17p (Latta and Hoo, 1974) and those of our own case seems to indicate a characteristic syndrome. The main features include a small-for-date baby born at full term, small stature, microcephaly, typical facial changes, a heart defect, contractures of different joints, and deformities of the feet. The patients show severe motor and mental retardation.