Johnson-McMillin syndrome: report of a new case with novel features

BACKGROUND: Johnson-McMillin syndrome (JMS) is a rare neuroectodermal disorder characterized by alopecia, ear malformations, conductive hearing loss, anosmia/hyposmia, and hypogonadotropic hypogonadism. It is inherited in an autosomal dominant manner; however, the causative gene has not yet been identified. CASE: Herein we report a patient with this condition who exhibits many of the features previously described, including alopecia, malformed auricles, conductive hearing loss, facial asymmetry, and developmental delays. Interestingly, she also has features that have not yet been reported, such as preauricular pits and tags, broad depressions at the lateral aspects of the eyes, and an abnormal left lower eyelid. CONCLUSIONS: In addition to demonstrating a pattern of anomalies consistent with JMS, this patient has several unique features. This phenotype supports the involvement of the branchial arches in the embryologic basis of this condition.     

Molecular cloning and expression of a novel CYP26 gene (cyp26d1) during zebrafish early development

Proper restriction of retinoid signaling by Cyp26s is essential for development of vertebrate embryos while inappropriate retinoid signaling can cause teratogenesis. Here, we report cloning and expression analysis of a novel cyp26 gene (cyp26d1) isolated from zebrafish. The predicted protein encoded by cyp26d1 consists of 554 amino acids. It exhibits 54% amino acid identity with human Cyp26C1, 50% with zebrafish Cyp26B1 and 38% with zebrafish Cyp26A1. Whole-mount in situ hybridization shows that cyp26d1 is first expressed in sphere stage, then disappears at 50% epiboly and resumes its expression at 75% epiboly. During segmentation period, cyp26d1 message is found at presumptive hindbrain. Double in situ hybridization with krox20 and cyp26d1 reveals that cyp26d1 is expressed in presumptive rhombomere 2-4 (r2-r4) at 2-somite stage. At 3-somite stage, cyp26d1 gene is expressed in r6 and pharyngeal arch (pa) one in addition to its expression at r2 and r4. At 6-somite stage, cyp26d1 message is present in continuous bands at r2-r6 and in pa1. This expression pattern is maintained from 10-somite stage through 21-somite stage except that the expression level is greatly reduced at r2 and r4. At 21-somite stage, cyp26d1 is also found in a group of cells in telencephalon and diencephalons. At 25-31h post-fertilization (hpf), the zebrafish cyp26d1 expression domain is extended to eyes, otic vesicles and midbrain in addition to its expression in hindbrain, telencephalon, diencephalons, and pharyngeal arches. At 35-48hpf, the expression of cyp26d1 is mainly restricted to otic vesicles, pharyngeal arches and pectoral fins and the expression level is greatly reduced.     

The chicken NKX2.8 homeobox gene: A novel member of the NK-2 gene family

 We have isolated the chicken homeobox gene NKX2.8, which represents a novel member of the NK-2 gene family. Besides the homeodomain, the NKX2.8 protein contains two other conserved sequences, a TN and an NK2 domain. NKX2.8 is expressed in the ventral foregut, the developing heart, in the epithelial layers of the branchial arches and in the dorsal mesocardium. Thus, its expression overlaps partially, but also differs significantly from another chicken tinman orthologue, the NKX2.5 gene. It is suggestive that NKX2.8 and NKX2.5 play a cooperative role in early heart development. Received: 28 January 1997 / Accepted: 8 February 1997     

儿童下牙弓发育的测量

本研究测量了１９３６名６－１２岁男女儿童的下颌牙弓的宽度和弦长。儿童前牙弓在７－９岁时增长最快,为此时恒尖牙萌出所致,１０岁以后各年龄组均数差异检验没有显著性意义。在整个替牙期,儿童前牙弓宽度约增加２ｍｍ,弦长增加１．８ｍｍ,儿童后牙弓的宽度和弦长约增加１ｍｍ左右。男孩前牙弓宽度比女孩大１ｍｍ左右。后牙弓的宽度和弦箕各年龄组均为男大于女,约１ｍｍ在右。可以把小学年龄阶段儿童的牙列分为乳牙弓、第１恒     

Ripply3 is required for the maintenance of epithelial sheets in the morphogenesis of pharyngeal pouches

During tissue development, the morphogenesis of epithelial sheets is regulated by many factors, including mechanical force, although the underlying mechanisms remain largely unknown. In the pharyngeal region of the vertebrate embryo, endodermal epithelium is reiteratively folded outward to form pharyngeal pouches, making partitions between the pharyngeal arches. Ripply3, encoding a member of the Ripply family of adaptor proteins, is required for the pouch formation posterior to the 2nd pharyngeal pouch. In this study, we found that the expression of mouse Ripply3 was specifically activated in accordance with the bending of the endodermal epithelium during the pouch formation. In Ripply3‐deficient embryos, a continuous monolayer of the endodermal epithelium was not maintained posterior to the 2nd pharyngeal pouch. Corresponding to the endodermal region of the deformed epithelium, the activated form of Integrin β1, which was localized at the basal side of the epithelial cells in the wild‐type embryos, was not persistently observed in the mutants. On the other hand, cell proliferation and apoptotic cell death in the endoderm were not obviously affected by the Ripply3 deficiency. Significantly, Ripply3 expressed in cultured cells was found to be preferentially accumulated in the focal adhesions, which are Integrin‐mediated adhesive contact sites transmitting mechanical force between the extracellular matrix and attached cells. Furthermore, Ripply3 promoted the maturation of focal adhesions in these cells. Thus, Ripply3 appears to have been activated to enhance the connection between the extracellular matrix and endodermal epithelial cells, as a mechanism to resist the mechanical stress generated during the bending of the epithelial sheets.     

Spondylolysis and its relationship to degenerative joint disease in the prehistoric southeastern United States

Spondylolysis, a fatigue fracture in the neural arch of lumbar vertebrae, is common in Eskimos and some athletes. In Archaic Indians from northwestern Alabama, 17% of males and 20% of females with complete lumbar regions showed this defect. It is found at a fairly early age in adult males in this group, but in females it does not appear until after age 40 years. Spondylolysis is associated with higher levels of osteoarthritis around the fifth lumbar vertebra, where this defect typically occurs. Otherwise, there is little relationship between its presence and degenerative joint disease, especially in the weight-bearing joints. The incidence in young males may be related to activities necessitating a high level of mobility around the lumbar spine. The late occurrence in females suggests that osteoporosis may have been a contributing factor.     

Organization of a phyllobranchiate gill from the green shore crab Carcinus maenas (Crustacea,Decapoda)

Summary The phyllobranchiate gills of the green shore crab Carcinus maenas have been examined histologically and ultrastructurally. Each gill lamella is bounded by a chitinous cuticle. The apical surface of the branchial epithelium contacts this cuticle, and a basal lamina segregates the epithelium from an intralamellar hemocoel. In animals acclimated to normal sea water, five epithelial cell types can be identified in the lamellae of the posterior gills: chief cells, striated cells, pillar cells, nephrocytes, and glycocytes. Chief cells are the predominant cells in the branchial epithelium. They are squamous or low cuboidal and likely play a role in respiration. Striated cells, which are probably involved in ionoregulation, are also squamous or low cuboidal. Basal folds of the striated cells contain mitochondria and interdigitate with the bodies and processes of adjacent cells. Pillar cells span the hemocoel to link the proximal and distal sides of a lamella. Nephrocytes are large, spherical cells with voluminous vacuoles. They are rimmed by foot processes or pedicels and frequently associate with the pillar cells. Glycocytes are pleomorphic cells packed with glycogen granules and multigranular rosettes. The glycocytes often mingle with the nephrocytes. Inclusion of the nephrocytes and glycocytes as members of the branchial epithelium is justified by their participation in intercellular junctions and their position internal to the epithelial basal lamina.     

Kinematic and Dynamic Characteristics of Pulsating Flow in 180^o Tube

Kinematic and dynamic characteristics of pulsating flow in a model of human aortic arch are obtained by a computational analysis. Three-dimensional flow processes are summarized by pressure distributions on the symmetric plane together with velocity and pressure contours on a few cross sections for systolic acceleration and deceleration. Without considering the effects of aortic tapering and the carotid arteries, the development of tubular boundary layer with centrifugal forces and pulsation are also analyzed for flow separation and backflow during systolic deceleration.     

Hox genes, neural crest cells and branchial arch patterning

Proper craniofacial development requires the orchestrated integration of multiple specialized tissue interactions. Recent analyses suggest that craniofacial development is not dependent upon neural crest pre-programming as previously thought but is regulated by a more complex integration of cell and tissue interactions. In the absence of neural crest cells it is still possible to obtain normal arch patterning indicating that neural crest is not responsible for patterning all of arch development. The mesoderm, endoderm and surface ectoderm tissues play a role in the patterning of the branchial arches, and there is now strong evidence that Hoxa2 acts as a selector gene for the pathways that govern second arch structures.     

Spatio‐temporal dynamics of gene expression of the Edn1‐Dlx5/6 pathway during development of the lower jaw

The morphogenesis of the vertebrate skull results from highly dynamic integrated processes involving the exchange of signals between the ectoderm, the endoderm, and cephalic neural crest cells (CNCCs). Before migration CNCCs are not committed to form any specific skull element, molecular signals exchanged in restricted regions of tissue interaction are crucial in providing positional identity to the CNCCs mesenchyme and activate the specific morphogenetic process of different skeletal components of the head. In particular, the endothelin‐1 (Edn1)‐dependent activation of Dlx5 and Dlx6 in CNCCs that colonize the first pharyngeal arch (PA1) is necessary and sufficient to specify maxillo‐mandibular identity. Here, to better analyze the spatio‐temporal dynamics of this process, we associate quantitative gene expression analysis with detailed examination of skeletal phenotypes resulting from combined allelic reduction of Edn1, Dlx5, and Dlx6. We show that Edn1‐dependent and ‐independent regulatory pathways act at different developmental times in distinct regions of PA1. The Edn1→Dlx5/6→Hand2 pathway is already active at E9.5 during early stages of CNCCs colonization. At later stages (E10.5) the scenario is more complex: we propose a model in which PA1 is subdivided into four adjacent territories in which distinct regulations are taking place. This new developmental model may provide a conceptual framework to interpret the craniofacial malformations present in several mouse mutants and in human first arch syndromes. More in general, our findings emphasize the importance of quantitative gene expression in the fine control of morphogenetic events. genesis 48:362–373, 2010. © 2010 Wiley‐Liss, Inc.