A prevalent Y;15 translocation in the Ethiopian Beta Israel community in Israel

We describe 7 cases of abnormal karyotypes involving chromosomes Y and 15 in Ethiopian Beta Israel patients: 46,XX, der(15)t(Y;15)(q12;p12) and 46,XY,der(15)t(Y;15)(q12;p12). Six cases were incidentally found in amniocentesis performed for various indications; the indication for karyotyping in 1 case was recurrent abortions. To the best of our knowledge, this is the first report of this translocation in a specific ethnic group. We conclude that the derivative chromosome 15 with chromosome Y is probably a normal variant in Ethiopian Beta Israel occurring at an estimated frequency of 4/74 (5.4%). The prenatal diagnosis of this translocation in this population probably does not require further parental testing.     

46,XX, der(15),t(Y;15)(q12;p11) karyotype in an azoospermic male

We report on a Yq/15p translocation in a 23-year-old infertile male referred for Klinefelter Syndrome testing, who had azoospermia and bilateral small testes. Hormonal studies revealed hypergonadotropic hypogonadism. Conventional cytogenetic procedures giemsa trypsin giemsa (GTG) and high resolution banding (HRB) and molecular cytogenetic techniques Fluorescence In Situ Hybridization (FISH) performed on high-resolution lymphocyte chromosomes revealed the karyotype 46,XX, t(Y;15)(q12;p11). SRY-gene was confirmed to be present by classical Polymerase Chain Reaction (PCR) methods. His father carried de novo derivative chromosome 15 [45,X, t(Y;15)(q12;p11)] and was fertile; the karyotype of the father using G-band technique confirmed a reciprocal balanced translocation between chromosome Y and 15. In the proband, the der (15) has been inherited from the father because the mother had a normal karyotype (46,XX). In the proband, the der (15) could have produced genetic imbalance leading to unbalanced robertson translocation between chromosome Y and 15, which might have resulted in azoospermia and infertility in the proband. The paternal translocation might have lead to formation of imbalanced ova, which might be resulted infertility in the proband. Sister''s karyotypes was normal (46,XX) while his brother was not analyzed.     

Coexistence of inverted Y, chromosome 15p+ and abnormal phenotype.

In this study, we report conventional and molecular cytogenetic studies in a patient with multiple anomalies who is a carrier of a pericentric inversion on chromosome Y and a chromosome 15p+. His parents were phenotypically normal. The father is a carrier of a pericentric inversion of chromosome Y, and the mother carries a large chromosome 15p+ variant. The inverted Y chromosome was demonstrated by GTG- and CBG-banding, and DAPI-staining. The presence of extra chromosomal material on the chromosome 15p, that was C-band and DAPI positive, was demonstrated by trypsin G-banding. This suggests that the extra chromosomal material contained repetitive DNA sequences. NOR-staining indicated the presence a nuclear organizer region at the junction of the chromosome 15p+ material. Fluorescence in situ hybridization (FISH), with chromosome X and Y painting probes, alpha- and classic-satellite probes specific for chromosome Y, alpha- and beta-satellite III probes for chromosome 15 were used to elucidate the nature of both the inverted Y chromosome and chromosome 15p+. The result with chromosome X and Y painting probes, alpha-satellite, classic-satellite, and DYS59 probes specific for chromosome Y revealed the rearrangement of the Y chromosome was an inv(Y)(p11.2q11.22 or q11.23). FISH with alpha-satellite and beta-satellite III probes for chromosome 15 demonstrated that the extra chromosomal material on the chromosome 15 probably represents beta-satellite III sequences. The possible roles of the simultaneous occurrence of an inverted Y and the amplified DNA sequence on chromosome 15p in the abnormal phenotype of the proband are discussed.     

A t(Y;15) translocation with a deletion of the proximal Yq in a boy with mixed gonadal dysgenesis

Summary A Japanese boy with genital malformation and mixed gonadal dysgenesis is described. The karyotype appeared to be 46,X t(15;Y)(p13;q11). A comparison of the Q-positive segment on der(15) with that of the paternal Y chromosome revealed, however, the loss of over half of the Q-positive segment from the paternal Y during t(15;Y) translocation. The father had an unusually long Y chromosome that corresponded to a chromosome 18. DNA analysis further revealed a deletion of the non-fluorescent part of the long arm of the Y chromosome spanning interval 5–6.     

A family case of fertile human 45,X,psu dic(15;Y) males

We report on a familial case including four male probands from three generations with a 45,X,psu dic(15;Y)(p11.2;q12) karyotype. 45,X is usually associated with a female phenotype and only rarely with maleness, due to translocation of small Y chromosomal fragments to autosomes. These male patients are commonly infertile because of missing azoospermia factor regions from the Y long arm. In our familial case we found a pseudodicentric translocation chromosome, that contains almost the entire chromosomes 15 and Y. The translocation took place in an unknown male ancestor of our probands and has no apparent effect on fertility and phenotype of the carrier. FISH analysis demonstrated the deletion of the pseudoautosomal region 2 (PAR2) from the Y chromosome and the loss of the nucleolus organizing region (NOR) from chromosome 15. The formation of the psu dic(15;Y) chromosome is a reciprocal event to the formation of the satellited Y chromosome (Yqs). Statistically, the formation of 45,X,psu dic(15;Y) (p11.2;q12) is as likely as the formation of Yqs. Nevertheless, it has not been described yet. This can be explained by the dicentricity of this translocation chromosome that usually leads to mitotic instability and meiotic imbalances. A second event, a stable inactivation of one of the two centromeres is obligatory to enable the transmission of the translocation chromosome and thus a stably reduced chromosome number from father to every son in this family.     

Molecular characterization of a Y;15 translocation segregating in a family

Summary We have used Y-specific and Y-derived DNA probes for in situ hybridization and Southern blotting analysis to characterize a Y;15 translocation showing normal Mendelian inheritance in a family. Cytogenetically there appeared to be an unbalanced translocation of Yqh to 15p; this translocation may be considered as a prototype of those translocations between Yq and the short arm of an acrocentric chromosome which have a population incidence of approximately 1 in 2,000. Our molecular studies showed that, in all probability, the breakpoints were near the border between Yq11.23 and Yq12, and in 15p11, respectively; the translocation is abbreviated t(Y;15)(q12;p11). Using the Y-specific probe pY431 in a quantitative Southern hybridization assay, normal females had no hybridization, female carriers and normal men had the same amount, and male carriers had twice that amount. Cytogenetic analysis and quantitative in situ hybridization using probes pY431 and pY3.4 were consistent with the hypothesis that the portion of Yq translocated to 15p comprised all of Yq12 and none of Yq11. The absence of Southern hybridization with probes specific for Yp and Yq11 confirmed this observation. Even though the family was ascertained through two brothers who both had schizophrenia and were carriers of the translocation, the clinical evaluation of a total of nine individuals with the translocation and five without it did not suggest its association with an abnormal phenotype.     

Y-chromosome DNA haplotype 15 in Europe.

Haplotype 15 at 1 Y-chromosome-specific DNA polymorphism (p49/TaqI) was reported in a meta-analysis concerning 2418 males originating from 28 different geographic locations in Western Europe. The highest frequency of haplotype 15 (72.2%) was observed in French Basques, and it was previously deduced that this haplotype is the ancestral haplotype in Europe (Lucotte and Hazout 1996). Percentages of haplotype 15 geographic distribution show another high frequency in northwestern Europeans and a gradient of decreasing frequencies toward southeastern and peripheral countries. These results suggest that frequencies of haplotype 15 of the Y chromosome are useful to study the contribution of pre-Neolithic males to the present-day populations of Europe.     

Robertsonian translocation between the chromosome Y and 15

Summary The Robertsonian translocation 45,X,t(Y;15q) was detected in four generations of male progeny. The karyotypes were studied by G-, Q-, and C-banding techniques. The chromosome Y involved in this translocation was of a short, nonfluorescent variant. The normal male phenotypes in all three adult translocation carriers (the great grandfather, the grandfather, and the father) support the hypothesis that the locus for the male determining factor is on the short arm of the chromosome Y.

---

Zusammenfassung Eine Robertsonsche Translokation 45,X,t(Y;15q) wurde in vier Generationen der männlichen Linie entdeckt. Die Karyotypen wurden mittels der G-, R- und C-Banding-Techniken untersucht. Das in diese Translokation verwickelte Y-Chromosom gehörte zu der kurzen, nichtfluorescierenden Variante. Alle Translokationsträger aus vier Generationen hatten einen normalen männlichen Phänotyp. Dadurch wird die Hypothese bestätigt, daß der Locus für den die Männlichkeit bestimmenden Faktor auf dem kurzen Arm des Y-Chromosoms gelegen ist.

     

Distinct functions of Cdk5(Y15) phosphorylation and Cdk5 activity in stress fiber formation and organization

Previous studies have shown that Cdk5 promotes lens epithelial cell adhesion. Here we use a cell spreading assay to investigate the mechanism of this effect. As cells spread, forming matrix adhesions and stress fibers, Cdk5(Y15) phosphorylation and Cdk5 kinase activity increased. Cdk5(Y15) phosphorylation was inhibited by PP1, a Src family kinase inhibitor. To identify the PP1-sensitive kinase, we transfected cells with siRNA oligonucleotides for cSrc and related kinases. Only cSrc siRNA oligonucleotides inhibited Cdk5(Y15) phosphorylation. Cdk5(pY15) and its activator, p35, colocalized with actin in stress fibers. To examine Cdk5 function, we inhibited Cdk5 activity under conditions that also prevent phosphorylation at Y15: expression of kinase inactive mutations Cdk5(Y15F) and Cdk5(K33T), and siRNA suppression of Cdk5. Stress fiber formation was severely inhibited. To distinguish between a requirement for Cdk5 kinase activity and a possible adaptor role for Cdk5(pY15), we used two methods that inhibit kinase activity without inhibiting phosphorylation at Y15: pharmacological inhibition with olomoucine and expression of the kinase inactive mutation, Cdk5(D144N). Stress fiber organization was altered, but stress fiber formation was not blocked. These findings indicate that Cdk5(Y15) phosphorylation and Cdk5 activity have distinct functions required for stress fiber formation and organization, respectively.     

Chk1 is a wee1 kinase in the G2 DNA damage checkpoint inhibiting cdc2 by Y15 phosphorylation.

The G2 DNA damage checkpoint ensures maintenance of cell viability by delaying progression into mitosis in cells which have suffered genomic damage. It is controlled by a number of proteins which are hypothesized to transduce signals through cell cycle regulators to delay activation of p34cdc2. Studies in mammalian cells have correlated induction of inhibitory tyrosine 15 (Y15) phosphorylation on p34cdc2 with the response to DNA damage. However, genetic studies in fission yeast have suggested that the major Y15 kinase, p107wee1, is not required for the cell cycle delay in response to DNA damage, although it is required for survival after irradiation. Thus, the target of the checkpoint, and hence the mechanism of cell cycle delay, remains unknown. We show here that Y15 phosphorylation is maintained in checkpoint-arrested fission yeast cells. Further, wee1 is required for cell cycle arrest induced by up-regulation of an essential component of this checkpoint, chk1. We observed that p107wee1 is hyperphosphorylated in cells delayed by chk1 overexpression or UV irradiation, and that p56chk1 can phosphorylate p107wee1 directly in vitro. These observations suggest that in response to DNA damage p107wee1 is phosphorylated by p56chk1 in vivo, and this results in maintenance of Y15 phosphorylation and hence G2 delay. In the absence of wee1, other Y15 kinases, such as p66mik1, may partially substitute for p107wee1 to induce cell cycle delay, but this wee1-independent delay is insufficient to maintain full viability. This study establishes a link between a G2 DNA damage checkpoint function and a core cell cycle regulator.     

Characterization of novel mutations at the Schizosaccharomyces pombe cdc2 regulatory phosphorylation site, tyrosine 15.

The cdc2 protein kinase family is regulated negatively by phosphorylation in the glycine ATP-binding loop at a conserved tyrosine residue, Y15, alone or in combination with T14 phosphorylation. In Schizosaccharomyces pombe and other systems, substitution of these residues with structurally similar but nonphosphorylatable amino acids has generated proteins (Y15F or T14AY15F) that behave as constitutively tyrosine-dephosphorylated proteins or threonine and tyrosine-dephosphorylated proteins. Here we report the characteristics of three additional mutants at Y15--Y15E, Y15S, and Y15T--in S. pombe cdc2p. All three mutant proteins are active in in vitro kinase assays, but are unable to functionally complement cdc2 loss-of-function mutations in vivo. Additionally, all three mutants are dominant negatives. A more detailed analysis of the Y15T mutant indicates that it can initiate chromosome condensation and F-actin contractile ring formation, but is unable to drive the reorganization of microtubules into a mitotic spindle.     

An endogenous electrophile that modulates the regulatory mechanism of protein turnover: inhibitory effects of 15-deoxy-Delta 12,14-prostaglandin J2 on proteasome

Prostaglandin D(2) (PGD(2)), a major cyclooxygenase product in a variety of tissues and cells, readily undergoes dehydration to yield electrophilic PGs, such as 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)). We have previously shown that 15d-PGJ(2) potently induces apoptosis of SH-SY5Y human neuroblastoma cells via accumulation of the tumor suppressor gene product p53. In the study presented here, we investigated the molecular mechanisms involved in the 15d-PGJ(2)-induced accumulation of p53. It was observed that 15d-PGJ(2) potently induced p53 protein expression but scarcely induced p53 gene expression. In addition, exposure of the cells to 15d-PGJ(2) resulted in an accumulation of ubiquitinated proteins and in a significant inhibition of proteasome activities, suggesting that 15d-PGJ(2) acted on the ubiquitin-proteasome pathway, a regulatory mechanism of p53 turnover. The effects of 15d-PGJ(2) on the protein turnover were attributed to its electrophilic feature, based on the observations that (i) the reduction of the double bond in the cyclopentenone ring of 15d-PGJ(2) virtually abolished the effects on protein turnover, (ii) overexpression of an endogenous redox regulator, thioredoxin 1, significantly retarded the inhibition of proteasome activities and accumulations of p53 and ubiquitinated proteins induced by 15d-PGJ(2), and (iii) treatment of SH-SY5Y cells with biotinylated 15d-PGJ(2) indeed resulted in the formation of a 15d-PGJ(2)-proteasome conjugate. These data suggest that the modulation of proteasome activity may be involved in the mechanism responsible for the accumulation of p53 and subsequent induction of apoptotic cell death induced by 15d-PGJ(2).     

Upregulated lncRNA small nucleolar RNA host gene 1 promotes 1-methyl-4-phenylpyridinium ion-induced cytotoxicity and reactive oxygen species production through miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells

Long noncoding RNA (lncRNA) small nucleolar RNA host gene 1 (SNHG1) has been demonstrated to be upregulated and play a crucial role in the pathology of Parkinson's disease (PD). However, the exact role of SNHG1 and its underlying mechanisms in PD remains elusive. In this study, we found that SNHG1 and glycogen synthase kinase 3 beta (GSK3β) were upregulated, but miR-15b-5p was downregulated in 1-methyl-4-phenylpyridinium ion (MPP⁺)-treated SH-SY5Y cells. The upregulation of SNHG1 enhanced MPP⁺-induced cellular toxicity in SH-SY5Y cells, as shown by decreased cell viability, increased ROS production, and increased number of TdT-mediated dUTP Nick-End labeling-positive cells, accompanied with the upregulation of cleaved caspase 3 and elevation of cytochrome C release. Meanwhile, SNHG1 knockdown presented the converse effects. SNHG1 was demonstrated to interact with miR-15b-5p. Moreover, SNHG1 could attenuate the inhibitory effects of miR-15b-5p on MPP⁺-induced cytotoxicity and production of ROS. Besides, GSK3β was identified as a direct target of miR-15b-5p. The inhibitory effects of SNHG1 knockdown or miR-15b-5p overexpression on MPP⁺-induced cytotoxicity and reactive oxygen species (ROS) production were abrogated by upregulation of GSK3β. Taken together, these results demonstrate that upregulated lncRNA SNHG1 promotes MPP⁺-induced cytotoxicity and ROS production through the miR-15b-5p/GSK3β axis in human dopaminergic SH-SY5Y cells, suggesting that SNHG1 may act as a potential therapeutic target for PD treatment in the future.     

Expression of DHA-Metabolizing Enzyme Alox15 is Regulated by Selective Histone Acetylation in Neuroblastoma Cells

The omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA) is enriched in neural membranes of the CNS, and recent studies have shown a role of DHA metabolism by 15-lipoxygenase-1 (Alox15) in prefrontal cortex resolvin D1 formation, hippocampo-prefrontal cortical long-term-potentiation, spatial working memory, and anti-nociception/anxiety. In this study, we elucidated epigenetic regulation of Alox15 via histone modifications in neuron-like cells. Treatment of undifferentiated SH-SY5Y human neuroblastoma cells with the histone deacetylase (HDAC) inhibitors trichostatin A (TSA) and sodium butyrate significantly increased Alox15 mRNA expression. Moreover, Alox15 expression was markedly upregulated by Class I HDAC inhibitors, MS-275 and depsipeptide. Co-treatment of undifferentiated SH-SY5Y cells with the p300 histone acetyltransferase (HAT) inhibitor C646 and TSA or sodium butyrate showed that p300 HAT inhibition modulated TSA or sodium butyrate-induced Alox15 upregulation. Differentiation of SH-SY5Y cells with retinoic acid resulted in increased neurite outgrowth and Alox15 mRNA expression, while co-treatment with the p300 HAT inhibitor C646 and retinoic acid modulated the increases, indicating a role of p300 HAT in differentiation-associated Alox15 upregulation. Increasing Alox15 expression was found in primary murine cortical neurons during development from 3 to 10 days-in-vitro, reaching high levels of expression by 10 days-in-vitro—when Alox15 was not further upregulated by HDAC inhibition. Together, results indicate regulation of Alox15 mRNA expression in neuroblastoma cells by histone modifications, and increasing Alox15 expression in differentiating neurons. It is possible that one of the environmental influences on the immature brain that can affect cognition and memory, may take the form of epigenetic effects on Alox15 and metabolites of DHA.     

Reassessment of presumed Y/22 and Y/15 translocations in man using a new technique.

A new chromosome banding technique, distamycin A plus DAPI, has been used to reexamine cases of presumed Y/autosome translocations. In contrast with the results obtained with quinacrine fluorescence (Q-banding), the satellites of acrocentric chromosomes do not fluoresce brightly with this new (DA-DAPI) method, making it more specific for the long arm of the Y chromosome. Previous cases with intensely Q-fluorescent and abnormally long short arms on a chromosome 22 were considered as presumptive 22/Y translocations: The new technique clearly shows that, in these cases, the additional material on 22p is not derived from Yq. In contrast, in other cases the Yq nature of additional material on 15p, in conjunction with the presence of an extra Y-body in interphase nuclei and the presence of a male-specific DNA, supports the previous diagnosis of a presumptive 15/Y translocation.     

A 45,X male with Y-specific DNA translocated onto chromosome 15.

A 20-year-old male patient with chromosomal constitution 45,X, testes and normal external genitalia was examined. Neither mosaicism nor a structurally aberrant Y chromosome was observed when routine cytogenetic analysis was performed on both lymphocytes and skin fibroblasts. Y chromosome-specific single-copy and repeated DNA sequences were detected in the patient's genome by means of 11 different recombinant-DNA probes of known regional assignment on the human Y chromosome. Data indicated that the short arm, the centromere, and part of the long-arm euchromatin of the Y chromosome have been retained and that the patient lacks deletion intervals 6 and 7 of Yq. High-resolution analysis of prometaphase chromosomes revealed additional euchromatic material on the short arm of one of the patient's chromosomes 15. After in situ hybridization with the Y chromosome-specific probe pDP105, a significant grain accumulation was observed distal to 15p11.2, suggesting a Y/15 chromosomal translocation. We conclude that some 45,X males originate from Y-chromosome/autosome translocations following a break in the proximal long arm of the Y chromosome.     

Identification and Clinical Implications of Novel MYO15A Mutations in a Non-consanguineous Korean Family by Targeted Exome Sequencing

Mutations of MYO15A are generally known to cause severe to profound hearing loss throughout all frequencies. Here, we found two novel MYO15A mutations, c.3871C>T (p.L1291F) and c.5835T>G (p.Y1945X) in an affected individual carrying congenital profound sensorineural hearing loss (SNHL) through targeted resequencing of 134 known deafness genes. The variant, p.L1291F and p.Y1945X, resided in the myosin motor and IQ2 domains, respectively. The p.L1291F variant was predicted to affect the structure of the actin-binding site from three-dimensional protein modeling, thereby interfering with the correct interaction between actin and myosin. From the literature analysis, mutations in the N-terminal domain were more frequently associated with residual hearing at low frequencies than mutations in the other regions of this gene. Therefore we suggest a hypothetical genotype-phenotype correlation whereby MYO15A mutations that affect domains other than the N-terminal domain, lead to profound SNHL throughout all frequencies and mutations that affect the N-terminal domain, result in residual hearing at low frequencies. This genotype-phenotype correlation suggests that preservation of residual hearing during auditory rehabilitation like cochlear implantation should be intended for those who carry mutations in the N-terminal domain and that individuals with mutations elsewhere in MYO15A require early cochlear implantation to timely initiate speech development.     

FISH Variants with D15Z1

We present our experience with cross-hybridization of D15Z1, used in combination with D15S10, D15S11 or SNRPN, in 109 clinical cases referred for Angelman syndrome (AS), Prader-Willi syndrome (PWS), for autism to rule out duplication of 15q11.2, or to identify structural chromosome abnormalities thought to involve chromosome 15. Nine cases with normal karyotypes studied with at least one of these probe mixtures showed an extra signal with D15Z1 on a chromosome 14. One case showed absence of the D15Z1 signal from 15p and one case showed an extra signal with D15Z1 on both chromosome 14s. Sixteen cases from this series had structural abnormalities, which included ten cases with supernumerary markers, three of which had a D15Z1 signal on a chromosome 14. The remaining cases did not have an extra signal on chromosome 14, but included rearrangements between Y and 15, 15 and 19, and a r(15), all with breakpoints in 15p11.1 or p11.2. Of the three cases with a supernumerary marker and an extra D15Z1 signal on a chromosome 14, one was a maternally derived marker, while the variant 14 was paternal in origin. The other two markers were de novo. The high frequency of variant 14 in cases with supernumerary markers (30%) was not significant by Chi-square analysis compared to the overall frequency in 109 cases of 11.9%. The overall frequency is consistent with a previous report by Stergianou et al. (1993). We can now add that a false-negative result may occur slightly less than 1% of the time. The chance that both chromosome 14 homologs will be positive for D15Z1 is theoretically about 1 in 300. If associated with an abnormal phenotype, the possibility of uniparental disomy should be ruled out.     

Involvement of the constitutive prostaglandin E synthase cPGES/p23 in expression of an initial prostaglandin E2 inactivating enzyme, 15-PGDH

We previously showed that cytosolic prostaglandin (PG) E synthase (cPGES/p23) which isomerizes PGH(2) to PGE(2), is essential for fetal mouse development. Embryonic fibroblasts derived from cPGES/p23 knockout mice generated higher amounts of PGE(2) in culture supernatants than wild-type-derived cells. In order to elucidate this apparent conflict that absence of PGE(2) synthetic enzyme caused facilitation of PGE(2) biosynthesis, we examined expression of the PGE(2) degrading enzyme in embryonic fibroblasts. We report here that embryonic fibroblasts deficient in cPGES/p23 decreased the expression of the PGE(2) degrading enzyme, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which catalyzes the inactivating conversion of the PGE(2) 15-OH to a 15-keto group, compared with that of wild-type. In addition, rat fibroblastic 3Y1 cells harboring cPGES/p23 siRNA exhibited lower 15-PGDH expression than mock-transfected cells. Furthermore, forcible expression of cPGES/p23 in 3Y1 cells resulted in facilitation of 15-PGDH promoter activity. These results suggest that the PGE(2)-inactivating pathway is controlled by the PGE(2) biosynthetic enzyme, cPGES/p23.