Targeted ablation of Wnt4 and Wnt5a in Müllerian duct mesenchyme impedes endometrial gland development and causes partial Müllerian agenesis.

Wnt4 and Wnt5a have well-established roles in the embryonic development of the female reproductive tract, as well as in implantation, decidualization, and ovarian function in adult mice. Although these roles appear to overlap, whether Wnt5a and Wnt4 are functionally redundant in these tissues has not been determined. We addressed this by concomitantly inactivating Wnt4 and Wnt5a in the Müllerian mesenchyme and in ovarian granulosa cells by crossing mice bearing floxed alleles to the Amhr2cre strain. Whereas fertility was reduced by ∼50% in Wnt4flox/flox; Amhr2cre/+ and Wnt5aflox/flox; Amhr2cre/+ females, Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice were either nearly or completely sterile. Loss of fertility was not due to an ovarian defect, as serum ovarian hormone levels, follicle counts, and ovulation rates were comparable to controls. Conversely, the uterus was abnormal in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice, with thin myometrial and stromal layers, frequent fibrosis and a >90% reduction in numbers of uterine glands, suggesting redundant or additive roles of Wnt4 and Wnt5a in uterine adenogenesis. Loss of fertility in Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ mice was attributed to defects in decidualization, implantation, and placental development, the severity of which were proportional to the extent of gland loss. Furthermore, a third of Wnt4flox/flox; Wnt5aflox/flox; Amhr2cre/+ females had a partial agenesis of Müllerian duct-derived structures, but with normal oviducts and ovaries. Together, our results suggest that Wnt4 and Wnt5a play redundant roles in the development of the female reproductive tract, and may provide insight into the etiology of certain cases of Müllerian agenesis in women.

MAPK/ERK Signaling in Regulation of Renal Differentiation.

Congenital anomalies of the kidney and urinary tract (CAKUT) are common birth defects derived from abnormalities in renal differentiation during embryogenesis. CAKUT is the major cause of end-stage renal disease and chronic kidney diseases in children, but its genetic causes remain largely unresolved. Here we discuss advances in the understanding of how mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) activity contributes to the regulation of ureteric bud branching morphogenesis, which dictates the final size, shape, and nephron number of the kidney. Recent studies also demonstrate that the MAPK/ERK pathway is directly involved in nephrogenesis, regulating both the maintenance and differentiation of the nephrogenic mesenchyme. Interestingly, aberrant MAPK/ERK signaling is linked to many cancers, and recent studies suggest it also plays a role in the most common pediatric renal cancer, Wilms' tumor.

Clock1a affects mesoderm development and primitive hematopoiesis by regulating Nodal-Smad3 signaling in the zebrafish embryo.

Circadian clock and Smad2/3/4-mediated Nodal signaling regulate multiple physiological and pathological processes. However, it remains unknown whether Clock directly cross-talks with Nodal signaling and how this would regulate embryonic development. Here we show that Clock1a coordinated mesoderm development and primitive hematopoiesis in zebrafish embryos by directly up-regulating Nodal-Smad3 signaling. We found that Clock1a is expressed both maternally and zygotically throughout early zebrafish development. We also noted that Clock1a alterations produce embryonic defects with shortened body length, lack of the ventral tail fin, or partial defect of the eyes. Clock1a regulates the expression of the mesodermal markers ntl, gsc, and eve1 and of the hematopoietic markers scl, lmo2, and fli1a Biochemical analyses revealed that Clock1a stimulates Nodal signaling by increasing expression of Smad2/3/4. Mechanistically, Clock1a activates the smad3a promoter via its E-box1 element (CAGATG). Taken together, these findings provide mechanistic insight into the role of Clock1a in the regulation of mesoderm development and primitive hematopoiesis via modulation of Nodal-Smad3 signaling and indicate that Smad3a is directly controlled by the circadian clock in zebrafish.

Clarification of mammalian cloacal morphogenesis using high-resolution episcopic microscopy.

The developmental process through which the cloaca transforms from one hollow structure to two separated urinary and digestive outlets remains controversial and speculative. Here, we use high-resolution episcopic microscopy to examine a comprehensive series of normal and mutant mouse cloaca in which the detailed 3-dimensional (3-D) morphological features are illuminated throughout the development. We provide evidence that the dorsal peri-cloacal mesenchyme (dPCM) remains stationary while other surrounding tissues grow towards it. This causes dramatic changes of spatial relationship among caudal structures and morphological transformation of the cloaca. The 3-D characterizations of Dkk1 mutants reveal a hyperplastic defect of dPCM, which leads to a significant anterior shift of the caudal boundary of the cloaca, premature occlusion of the cloaca and, imperforate anus phenotype. Conversely, Shh knockout causes a severe hypoplastic defect of cloaca mesenchyme including dPCM and persistent cloaca. Collectively, these findings suggest that formation of the dPCM is critical for cloacal morphogenesis and furthermore, growth and movement of the mesenchymal tissues towards the dPCM lead to the cloaca occlusion and separation of the urinary and digestive outlets.

Mesodermal ALK5 controls lung myofibroblast versus lipofibroblast cell fate.

BACKGROUND: Epithelial-mesenchymal cross talk is centerpiece in the development of many branched organs, including the lungs. The embryonic lung mesoderm provides instructional information not only for lung architectural development, but also for patterning, commitment and differentiation of its many highly specialized cell types. The mesoderm also serves as a reservoir of progenitors for generation of differentiated mesenchymal cell types that include αSMA-expressing fibroblasts, lipofibroblasts, endothelial cells and others. Transforming Growth Factor ß (TGFß) is a key signaling pathway in epithelial-mesenchymal cross talk. Using a cre-loxP approach we have elucidated the role of the TGFß type I receptor tyrosine kinase, ALK5, in epithelial-mesenchymal cross talk during lung morphogenesis. RESULTS: Targeted early inactivation of Alk5 in mesodermal progenitors caused abnormal development and maturation of the lung that included reduced physical size of the sub-mesothelial mesoderm, an established source of specific mesodermal progenitors. Abrogation of mesodermal ALK5-mediated signaling also inhibited differentiation of cell populations in the epithelial and endothelial lineages. Importantly, Alk5 mutant lungs contained a reduced number of αSMA(pos) cells and correspondingly increased lipofibroblasts. Elucidation of the underlying mechanisms revealed that through direct and indirect modulation of target signaling pathways and transcription factors, including PDGFRα, PPARγ, PRRX1, and ZFP423, ALK5-mediated TGFß controls a process that regulates the commitment and differentiation of αSMA(pos) versus lipofibroblast cell populations during lung development. CONCLUSION: ALK5-mediated TGFß signaling controls an early pathway that regulates the commitment and differentiation of αSMA(pos) versus LIF cell lineages during lung development.

The hSSB1 orthologue Obfc2b is essential for skeletogenesis but dispensable for the DNA damage response in vivo.

Human single-stranded DNA-binding protein 1 (hSSB1), encoded by OBFC2B, was recently characterized as an essential factor for the initiation of DNA damage checkpoints and the maintenance of genomic stability. Here, we report that loss of Obfc2b in mice results in perinatal lethality characterized by growth delay and skeletal abnormalities. These abnormalities are associated with accumulation of γH2ax, apoptosis and defective pre-cartilage condensation, which is essential for normal bone formation. However, deficiency of Obfc2b does not affect the initiation of DNA damage checkpoints, Atm activation, or the maintenance of genomic stability in B lymphocytes and primary fibroblasts. Loss of Obfc2b results in increased expression of its homologue Obfc2a (hSSB2). In contrast to Obfc2b deficiency, depletion of Obfc2a in fibroblasts results in impaired proliferation, accumulation of γH2ax and increased genomic instability. Thus, the hSSB1 orthologue Obfc2b has a unique function during embryogenesis limited to cell types that contribute to bone formation. While being dispensable in most other cell lineages, its absence leads to a compensatory increase in Obfc2a protein, a homologue required for the maintenance of genomic integrity.

A retrotransposon insertion in the 5' regulatory domain of Ptf1a results in ectopic gene expression and multiple congenital defects in Danforth's short tail mouse.

Danforth's short tail mutant (Sd) mouse, first described in 1930, is a classic spontaneous mutant exhibiting defects of the axial skeleton, hindgut, and urogenital system. We used meiotic mapping in 1,497 segregants to localize the mutation to a 42.8-kb intergenic segment on chromosome 2. Resequencing of this region identified an 8.5-kb early retrotransposon (ETn) insertion within the highly conserved regulatory sequences upstream of Pancreas Specific Transcription Factor, 1a (Ptf1a). This mutation resulted in up to tenfold increased expression of Ptf1a as compared to wild-type embryos at E9.5 but no detectable changes in the expression levels of other neighboring genes. At E9.5, Sd mutants exhibit ectopic Ptf1a expression in embryonic progenitors of every organ that will manifest a developmental defect: the notochord, the hindgut, and the mesonephric ducts. Moreover, at E 8.5, Sd mutant mice exhibit ectopic Ptf1a expression in the lateral plate mesoderm, tail bud mesenchyme, and in the notochord, preceding the onset of visible defects such as notochord degeneration. The Sd heterozygote phenotype was not ameliorated by Ptf1a haploinsufficiency, further suggesting that the developmental defects result from ectopic expression of Ptf1a. These data identify disruption of the spatio-temporal pattern of Ptf1a expression as the unifying mechanism underlying the multiple congenital defects in Danforth's short tail mouse. This striking example of an enhancer mutation resulting in profound developmental defects suggests that disruption of conserved regulatory elements may also contribute to human malformation syndromes.

Mesenchymal adenomatous polyposis coli plays critical and diverse roles in regulating lung development.

BACKGROUND: Adenomatous polyposis coli (Apc) is a tumor suppressor that inhibits Wnt/Ctnnb1. Mutations of Apc will not only lead to familial adenomatous polyposis with associated epithelial lesions, but will also cause aggressive fibromatosis in mesenchymal cells. However, the roles of Apc in regulating mesenchymal cell biology and organogenesis during development are unknown. RESULTS: We have specifically deleted the Apc gene in lung mesenchymal cells during early lung development in mice. Loss of Apc function resulted in immediate mesenchymal cell hyperproliferation through abnormal activation of Wnt/Ctnnb1, followed by a subsequent inhibition of cell proliferation due to cell cycle arrest at G0/G1, which was caused by a mechanism independent of Wnt/Ctnnb1. Meanwhile, abrogation of Apc also disrupted lung mesenchymal cell differentiation, including decreased airway and vascular smooth muscle cells, the presence of Sox9-positive mesenchymal cells in the peripheral lung, and excessive versican production. Moreover, lung epithelial branching morphogenesis was drastically inhibited due to disrupted Bmp4-Fgf10 morphogen production and regulation in surrounding lung mesenchyme. Lastly, lung mesenchyme-specific Apc conditional knockout also resulted in altered lung vasculogenesis and disrupted pulmonary vascular continuity through a paracrine mechanism, leading to massive pulmonary hemorrhage and lethality at mid-gestation when the pulmonary circulation should have started. CONCLUSIONS: Our study suggests that Apc in lung mesenchyme plays central roles in coordinating the proper development of several quite different cellular compartments including lung epithelial branching and pulmonary vascular circulation during lung organogenesis.

Fgfr2 is integral for bladder mesenchyme patterning and function.

While urothelial signals, including sonic hedgehog (Shh), drive bladder mesenchyme differentiation, it is unclear which pathways within the mesenchyme are critical for its development. Studies have shown that fibroblast growth factor receptor (Fgfr)2 is necessary for kidney and ureter mesenchymal development. The objective of the present study was to determine the role of Fgfr2 in the bladder mesenchyme. We used Tbx18cre mice to delete Fgfr2 in the bladder mesenchyme (Fgfr2(BM-/-)). We performed three-dimensional reconstructions, quantitative real-time PCR, in situ hybridization, immunolabeling, ELISAs, immunoblot analysis, void stain on paper, ex vivo bladder sheet assays, and in vivo decerebrated cystometry. Compared with control bladders, embryonic day 16.5 (E16.5) Fgfr2(BM-/-) bladders had thin muscle layers with less α-smooth muscle actin and thickened lamina propria with increased collagen type Ia and IIIa that intruded into the muscle. The reciprocal changes in mutant layer thicknesses appeared partly due to a cell fate switch. From postnatal days 1 to 30, Fgfr2(BM-/-) bladders demonstrated progressive muscle loss and increased collagen expression. Postnatal Fgfr2(BM-/-) bladder sheets exhibited decreased agonist-mediated contractility and increased passive stretch tension versus control bladder sheets. Cystometry revealed high baseline and threshold pressures and shortened intercontractile intervals in Fgfr2(BM-/-) versus control bladders. Mechanistically, whereas Shh expression appeared normal, mRNA and protein readouts of hedgehog activity were increased in E16.5 Fgfr2(BM-/-) versus control bladders. Moreover, E16.5 Fgfr2(BM-/-) bladders exhibited higher levels of Cdo and Boc, hedgehog coreceptors that enhance sensitivity to Shh, compared with control bladders. In conclusion, loss of Fgfr2 in the bladder mesenchyme leads to abnormal bladder morphology and decreased compliance and contractility.

Dicer function is required in the metanephric mesenchyme for early kidney development.

MicroRNAs (miRNAs) are small, noncoding regulatory RNAs that act as posttranscriptional repressors by binding to the 3'-untranslated region (3'-UTR) of target genes. They require processing by Dicer, an RNase III enzyme, to become mature regulatory RNAs. Previous work from our laboratory revealed critical roles for miRNAs in nephron progenitors at midgestation (Ho J, Pandey P, Schatton T, Sims-Lucas S, Khalid M, Frank MH, Hartwig S, Kreidberg JA. J Am Soc Nephrol 22: 1053-1063, 2011). To interrogate roles for miRNAs in the early metanephric mesenchyme, which gives rise to nephron progenitors as well as the renal stroma during kidney development, we conditionally ablated Dicer function in this lineage. Despite normal ureteric bud outgrowth and condensation of the metanephric mesenchyme to form nephron progenitors, early loss of miRNAs in the metanephric mesenchyme resulted in severe renal dysgenesis. Nephron progenitors are initially correctly specified in the mutant kidneys, with normal expression of several transcription factors known to be critical in progenitors, including Six2, Pax2, Sall1, and Wt1. However, there is premature loss of the nephron progenitor marker Cited1, marked apoptosis, and increased expression of the proapoptotic protein Bim shortly after the initial inductive events in early kidney development. Subsequently, there is a failure in ureteric bud branching and nephron progenitor differentiation. Taken together, our data demonstrate a previously undetermined requirement for miRNAs during early kidney organogenesis and indicate a crucial role for miRNAs in regulating the survival of this lineage.

A nondysraphic paraspinal mass and a ventricular septal defect: unusual components of diabetes-induced mesodermal derangement.

Solitary paraspinal masses in the pediatric age group commonly occur secondary to spinal dysraphism, chronic inflammatory conditions, and tumors. We describe the unusual case of a 10-year-old boy with a nondysraphic, paraspinal mass that had occurred secondary to congenital spinal epidural lipomatosis (SEL) in the setting of poorly controlled maternal type-I diabetes mellitus. The mass was picked up along with a ventricular septal defect (VSD) on an antenatal ultrasonogram. This is the first report in literature of SEL presenting as a solitary paraspinal mass at birth, and in the unusual setting of an antenatal mesodermal derangement that simultaneously engendered a VSD.

Enhanced Canonical Wnt Signaling During Early Zebrafish Development Perturbs the Interaction of Cardiac Mesoderm and Pharyngeal Endoderm and Causes Thyroid Specification Defects.

Background: Congenital hypothyroidism due to thyroid dysgenesis is a frequent congenital endocrine disorder for which the molecular mechanisms remain unresolved in the majority of cases. This situation reflects, in part, our still limited knowledge about the mechanisms involved in the early steps of thyroid specification from the endoderm, in particular the extrinsic signaling cues that regulate foregut endoderm patterning. In this study, we used small molecules and genetic zebrafish models to characterize the role of various signaling pathways in thyroid specification. Methods: We treated zebrafish embryos during different developmental periods with small-molecule compounds known to manipulate the activity of Wnt signaling pathway and observed effects in thyroid, endoderm, and cardiovascular development using whole-mount in situ hybridization and transgenic fluorescent reporter models. We used the antisense morpholino (MO) technique to create a zebrafish acardiac model. For thyroid rescue experiments, bone morphogenetic protein (BMP) pathway induction in zebrafish embryos was obtained by manipulation of heat-shock inducible transgenic lines. Results: Combined analyses of thyroid and cardiovascular development revealed that overactivation of Wnt signaling during early development leads to impaired thyroid specification concurrent with severe defects in the cardiac specification. When using a model of MO-induced blockage of cardiomyocyte differentiation, a similar correlation was observed, suggesting that defective signaling between cardiac mesoderm and endodermal thyroid precursors contributes to thyroid specification impairment. Rescue experiments through transient overactivation of BMP signaling could partially restore thyroid specification in models with defective cardiac development. Conclusion: Collectively, our results indicate that BMP signaling is critically required for thyroid cell specification and identify cardiac mesoderm as a likely source of BMP signals.

High incidence of vesicoureteral reflux in mice with Fgfr2 deletion in kidney mesenchyma.

PURPOSE: Mice with Fgfr2 conditional deletion in metanephric mesenchyma (Fgfr2(Mes-/-)) have ureteral bud induction abnormalities. We determined whether Fgfr2(Mes-/-) mutants developed abnormally positioned ureters predisposing to vesicoureteral reflux. MATERIALS AND METHODS: We measured common nephric duct length and assayed for apoptosis in embryonic day 11.5 mice. We performed 3-dimensional reconstruction of, and real-time polymerase chain reaction and whole mount in situ hybridization for Fgfr2 in urinary tracts in embryonic day 15.5 embryos. We also performed cystograms followed by 3-dimensional reconstruction in postnatal animals. RESULTS: Compared with controls Fgfr2(Mes-/-) embryos had increased common nephric duct length with no difference in apoptosis, indicating cranially displaced ureteral buds. Three-dimensional reconstruction at embryonic day 15.5 showed low ureteral insertion into the bladder near the bladder neck in Fgfr2(Mes-/-) mice. Postnatal Fgfr2(Mes-/-) mutants had a high rate of vesicoureteral reflux compared with controls (47.4% vs 4.0%, p = 0.00006). In postnatal mutants with unilateral reflux the refluxing ureters inserted closer to the bladder neck than nonrefluxing ureters. External ureteral insertional angles at the outer bladder wall formed by the ureteral insertion points and the bladder neck were greater in mutant refluxing ureters than in contralateral nonrefluxing ureters or control ureters. At embryonic day 15.5 Fgfr2 was decreased in Fgfr2(Mes-/-) kidneys compared with that in controls but not statistically different in ureters or bladders. CONCLUSIONS: Fgfr2(Mes-/-) mice have ureteral induction abnormalities associated with abnormal ureteral insertion in the bladder and subsequent vesicoureteral reflux, consistent with the Mackie and Stephens hypothesis.

Distinct roles and regulations for HoxD genes in metanephric kidney development.

Hox genes encode homeodomain-containing proteins that control embryonic development in multiple contexts. Up to 30 Hox genes, distributed among all four clusters, are expressed during mammalian kidney morphogenesis, but functional redundancy between them has made a detailed functional account difficult to achieve. We have investigated the role of the HoxD cluster through comparative molecular embryological analysis of a set of mouse strains carrying targeted genomic rearrangements such as deletions, duplications, and inversions. This analysis allowed us to uncover and genetically dissect the complex role of the HoxD cluster. Regulation of metanephric mesenchyme-ureteric bud interactions and maintenance of structural integrity of tubular epithelia are differentially controlled by some Hoxd genes during renal development, consistent with their specific expression profiles. We also provide evidence for a kidney-specific form of colinearity that underlies the differential expression of two distinct sets of genes located on both sides and overlapping at the Hoxd9 locus. These insights further our knowledge of the genetic control of kidney morphogenesis and may contribute to understanding certain congenital kidney malformations, including polycystic kidney disease and renal hypoplasia.

Three-dimensional imaging reveals ureteric and mesenchymal defects in Fgfr2-mutant kidneys.

Current techniques to morphologically characterize the processes of nephrogenesis and ureteric branching during kidney development have many limitations. Here, we used in vivo three-dimensional analysis to study renal development in mice lacking fibroblast growth factor receptor 2 in the ureteric bud (Fgfr2(UB-/-)) and in littermate controls. We found that Fgfr2(UB-/-) mice have more severe defects in ureteric branching morphogenesis than previously reported, including significantly fewer branches and tips than control mice. Furthermore, these mice had decreased ureteric volume and surface area and longer ureteric segments than control mice. We also observed previously unrecognized abnormalities in nephrogenesis, including a gradual increase in volume and surface area during maturation from renal vesicles to mature nephrons, in the mutant mice. Finally, we quantified many events of normal renal development that are either difficult or impossible to measure without this three-dimensional technique. In summary, the three-dimensional approach is a powerful and quantitative means to characterize branching morphogenesis and nephrogenesis.

A case of lower mesodermal defects sequence.

Here, we describe a stillborn fetus who had lower mesodermal defects sequence associated with craniorachischisis, anencephaly, bilateral pulmonary hypoplasia.

Oct4 plays a role in 2, 3, 7, 8 - tetrachlorobenzo-p-dioxin (TCDD) inducing cleft palate and inhibiting mesenchymal proliferation.

As a common birth defect, Cleft palate can be caused by the disturbance during the developmental process of the palatal shelves. The 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) is a well-known environmental teratogenic agent for cleft palate and Aryl hydrocarbon receptor (AhR) pathway can be activated by dioxins. Oct4 as a pluripotent stem cell transcription factor is also involved in the process of embryonic development. The AHR and retinoid receptors have cross-talk at CYP1A1 (cytochrome P450, family 1, subfamily A, polypeptide 1) promoter. There are also bidirectional talk between AhR and Oct4. In this study, we used C57/BL6 N mice and TCDD (64 µg/Kg body weight) to establish a model of fetal cleft palate to observe the effects of dioxin on fetal mesenchymal proliferation and apoptosis, and explore the role of Oct4 in inducing cleft palate. The results showed that dioxin inhibited mesenchymal proliferation and promoted apoptosis. In addition, dioxin inhibited Oct4 expression, and preliminary data suggest that hypermethylation of the Oct4 promoter may be a putative mechanism, suggesting that TCDD might induce cleft palate by inhibiting the proliferation of palatal mesenchymal cells mediated by Oct4.

An absence of Twist1 results in aberrant cardiac neural crest morphogenesis.

The basic helix-loop-helix transcription factor Twist1 plays an essential role in mesenchymal cell populations during embryonic development and in pathological disease. Remodeling of the cardiac outflow tract (OFT) into the functionally separate aortic arch and pulmonary trunk is dependent upon the dynamic, coordinated contribution of multiple mesenchymal cell populations. Here, we report that Twist1(-/-) mice exhibit OFTs that contain amorphic cellular nodules within their OFT endocardial cushions. The nodular mesenchyme expresses the related bHLH factors Hand1 and Hand2, but reduced levels of the normal cushion marker Periostin. Lineage mapping confirms that nodule cells are exclusively of cardiac neural crest origin (cNCC), and are not ectopic cardiomyocytes or smooth muscle cells. These studies also reveal a delay in cNCC colonization of the OFT cushions. Furthermore, these mapping studies uncover nodules in the pharyngeal arches, and identify Twist1(-/-) neural crest cell defects within the dorsal neural tube, which exhibits an expanded domain of Wnt1-Cre-lineage marked cells. Together, these data support a model where Twist1 is required both for proper cNCC delamination, and for emigration from the dorsal neural tube and along cNCC migration pathways. Within the Twist1(-/-) neural crest cell populations that do emigrate to the OFT, a Hand-expressing subpopulation displays defective maturation, tracking, and, presumably, cell-cell adhesion, further compromising cNCC morphogenesis.

Microarray analysis of murine limb bud ectoderm and mesoderm after exposure to cadmium or acetazolamide.

BACKGROUND: A variety of drugs, environmental chemicals, and physical agents induce a common limb malformation in the offspring of pregnant mice exposed on day 9 of gestation. This malformation, postaxial, right-sided forelimb ectrodactyly, is thought to arise via an alteration of hedgehog signaling. METHODS: We have studied two of these teratogens, acetazolamide and cadmium, using the technique of microarray analysis of limb bud ectoderm and mesoderm to search for changes in gene expression that could indicate a common pathway to postaxial limb reduction. RESULTS: Results indicated a generalized up-regulation of gene expression after exposure to acetazolamide but a generalized down-regulation due to cadmium exposure. An intriguing observation was a cadmium-induced reduction of Mt1 and Mt2 expression in the limb bud mesoderm indicating a lowering of embryonic zinc. CONCLUSIONS: We propose that these two teratogens and others (valproic acid and ethanol) lower sonic hedgehog signaling by perturbation of zinc function in the sonic hedgehog protein.

Axial Mesodermal Dysplasia Complex with a Unique Abnormal Course of Vestibulocochlear Nerve.

Axial mesodermal dysplasia complex (AMDC) is a combination of multiple congenital malformations arising due to the mesodermal cell migration, neural tube fusion, and rhombencephalon segmentation. Here, we present the imaging findings of a 15-year-old boy with AMDC who has bilateral inner ear malformations associated with a vestibulocochlear nerve extending to Meckel cave, cystic lesion in prepontine cisterna, cervical vertebral segmentation anomalies, and maxillar bone anomalies.