Characterization of chromosomal inversion of the mouse hairy ears (Eh) mutation associated with cleft palate

Gene datasets associated with mouse cleft palate

This article presents data on genes associated with cleft palate (CP), retrieved through both a full-text systematic review and a mouse genome informatics (MGI) database search. In order to group CP-associated genes according to function, pathway, biological process, and cellular component, the genes were analyzed using category enrichment bioinformatics tools, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO). This approach provides invaluable opportunities for the identification of candidate pathways and genes in CP research.

Homeobox family Hoxc localization during murine palate formation

Homeobox genes play important roles in craniofacial morphogenesis. However, the characteristics of the transcription factor Hoxc during palate formation remain unclear. We examined the immunolocalization patterns of Hoxc5, Hoxc4, and Hoxc6 in palatogenesis of cleft palate (Eh/Eh) mice. On the other hand, mutations in the FGF/FGFR pathway are exclusively associated with syndromic forms of cleft palate. We also examined the immunolocalization of Fgfr1 and Erk1/2 to clarify their relationships with Hoxc in palatogenesis. Some palatal epithelial cells showed Hoxc5 labeling, while almost no labeling of mesenchymal cells was observed in +/+ mice. As palate formation progressed in +/+ mice, Hoxc5, Hoxc4, and Hoxc6 were observed in medial epithelial seam cells. Hoxc5 and Hoxc6 were detected in the oral epithelium. The palatal mesenchyme also showed intense staining for Fgfr1 and Erk1/2 with progression of palate formation. In contrast, the palatal shelves of Eh/Eh mice exhibited impaired horizontal growth and failed to fuse, resulting in a cleft. Hoxc5 was observed in a few epithelial cells and diffusely in the mesenchyme of Eh/Eh palatal shelves. No or little labeling of Fgfr1 and Erk1/2 was detected in the cleft palate of Eh/Eh mice. These findings suggest that Hoxc genes are involved in palatogenesis. Furthermore, there may be the differences in the localization pattern between Hoxc5, Hoxc4, and Hoxc6. Additionally, Hoxc distribution in palatal cells during palate development may be correlated with FGF signaling. (228/250 words) © 2016 Japanese Teratology Society.

Upregulation of Nicotinic Acetylcholine Receptor alph4+beta2 through a Ligand-Independent PI3Kbeta Mechanism That Is Enhanced by TNFalpha and the Jak2/p38Mapk Pathways

High affinity nicotine-binding sites in the mammalian brain are neuronal nicotinic acetylcholine receptors (nAChR) assembled from at least alpha4 and beta2 subunits into pentameric ion channels. When exposed to ligands such as nicotine, these receptors respond by undergoing upregulation, a correlate of nicotine addiction. Upregulation can be measured using HEK293 (293) cells that stably express alpha4 and beta2 subunits using quantification of [³H]epibatidine ([³H]Eb) binding to measure mature receptors. Treatment of these cells with choline also produces upregulation through a hemicholinium3 (HC3)-sensitive (choline kinase) and an HC3-insensitive pathway which are both independent of the mechanism used by nicotine for upregulation. In both cases, upregulation is significantly enhanced by the pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) which signals through its receptor Tnfr1 to activate p38Mapk. Here we report that the inhibition of class1 phosphoinositide 3-kinases isoform PI3Kbeta using the selective antagonist PI828 is alone sufficient to produce upregulation and enhance both nicotine and choline HC3-sensitive mediated upregulation. Further, these processes are impacted upon by an AG-490 sensitive Jak2-associated pathway. Both PI3Kbeta (negative) and Jak2 (positive) modulation of upregulation converge through p38Mapk and both overlap with TNFalpha enhancement of this process. Upregulation through the PI3Kbeta pathway did not require Akt. Collectively these findings support upregulation of endogenous alpha4beta2 as a balance among cellular signaling networks that are highly responsive to multiple environmental, inflammatory and metabolic agents. The findings also suggest how illness and metabolic stress could alter the expression of this important nicotinic receptor and novel avenues to intercede in modifying its expression.

Insertional mutation in the Golgb1 gene is associated with osteochondrodysplasia and systemic edema in the OCD rat

Homozygous rats (ocd/ocd) of a mutant inbred strain, OCD (osteochondrodysplasia), show osteochondrodysplasia, systemic edema, cleft palate, protruding tongue, disproportionate dwarfism, and lethality immediately after birth. Their epiphyses show decreased levels of glycosaminoglycans and weak staining for extracellular matrix proteins. The epiphyseal chondrocytes have large vesicles and expanded endoplasmic reticulum and Golgi apparatus. These phenotypic features are inherited in an autosomal recessive manner, and the ocd locus responsible for these phenotypes has been mapped close to D11Mgh3 on rat chromosome 11. In the present study, we characterized the embryonic pathogenesis of ocd/ocd rats and identified the mutant gene. Subcutaneous edema in the dorsal portion was found at embryonic day (E) 16.5, and the other anomalies described above were apparent after E18.5 in ocd/ocd. Whole mount immunohistochemistry for Sox9 revealed that mesenchymal condensation was delayed in limb bud in ocd/ocd, and skeletal preparation showed that the progression of whole-body chondrogenesis was delayed in ocd/ocd. Histological and immunohistological analyses of the femur showed that cell proliferations of resting and proliferative zones of growth plate were significantly reduced in ocd/ocd embryos. Fine linkage mapping localized the ocd locus within 84kb of positions 65,584-65,668kb containing a part of Golgb1 gene on chromosome 11. Expression of Golgb1 mRNA was found in limb buds, somite derivatives and calvaria. Sequence analysis identified a 10-bp insertion in exon 13 of the Golgb1 gene in ocd/ocd rats. The Golgb1 gene encodes the COPI vesicle tethering factor, giantin. This insertion mutation causes a frame shift, and introduces a premature termination codon at codon 1082, leading to truncation of the C-terminal two thirds of giantin. By in-gel Western analysis using anti-giantin antibody that recognizes an epitope within 200 aa of the C-terminus, the expression of giantin was not detected in ocd/ocd embryos. As the C-terminal region of giantin is required for localization to the Golgi apparatus, these results strongly suggested that giantin is functionally defective in ocd/ocd rats. Therefore, we concluded that mutation of the Golgb1 gene is responsible for the phenotypic characteristics including osteochondrodysplasia of ocd/ocd, and that giantin plays a pivotal role in multiple aspects of chondrogenesis.

Characterization of the chromosomal inversion associated with the Koa mutation in the mouse revealed the cause of skeletal abnormalities

BACKGROUND

Koala (Koa) is a dominant mutation in mice causing bushy muzzle and pinna, and is associated with a chromosomal inversion on the distal half of chromosome 15. To identify the gene responsible for the Koa phenotypes, we investigated phenotypes of Koa homozygous mice and determined the breakpoints of the inversion with a genetic method using recombination between two different chromosomal inversions.

RESULTS

Skeletal preparation of Koa homozygotes showed marked deformity of the ribs and a wider skull with extended zygomatic arches, in addition to a general reduction in the lengths of long bones. They also had open eyelids at birth caused by a defect in the extension of eyelid anlagen during the embryonic stages. The proximal and distal breakpoints of the Koa inversion were determined to be 0.8-Mb distal to the Trsps1 gene and to 0.1-Mb distal to the Hoxc4 gene, respectively, as previously reported. The phenotypes of mice with the recombinant inverted chromosomes revealed the localization of the gene responsible the Koa phenotype in the vicinity of the proximal recombinant breakpoint. Expression of the Trsps1 gene in this region was significantly reduced in the Koa homozygous and heterozygous embryos.

CONCLUSION

While no gene was disrupted by the chromosomal inversion, an association between the Koa phenotype and the proximal recombinant breakpoint, phenotypic similarities with Trps1-deficient mice or human patients with TRSP1 mutations, and the reduced expression of the Trsps1 gene in Koa mice, indicated that the phenotypes of the Koa mice are caused by the altered expression of the Trps1 gene.

A position effect on TRPS1 is associated with Ambras syndrome in humans and the Koala phenotype in mice

Ambras syndrome (AS) is a rare form of congenital hypertrichosis with excessive hair on the shoulders, face and ears. Cytogenetic studies have previously implicated an association with rearrangements of chromosome 8. Here we define an 11.5 Mb candidate interval for AS on chromosome 8q based on cytogenetic breakpoints in three patients. TRPS1, a gene within this interval, was deleted in a patient with an 8q23 chromosomal rearrangement, while its expression was significantly downregulated in another patient with an inversion breakpoint 7.3 Mb downstream of TRPS1. Here, we describe the first potential long-range position effect on the expression of TRPS1. To gain insight into the mechanisms by which Trps1 affects the hair follicle, we performed a detailed analysis of the hair abnormalities in Koa mice, a mouse model of hypertrichosis. We found that the proximal breakpoint of the Koa inversion is located 791 kb upstream of Trps1. Quantitative real-time polymerase chain reaction, in situ hybridization and immunofluorescence analysis revealed that Trps1 expression levels are reduced in Koa mutant mice at the sites of pathology for the phenotype. We determined that the Koa inversion creates a new Sp1 binding site and translocates additional Sp1 binding sites within a highly conserved stretch spanning the proximal breakpoint, providing a potential mechanism for the position effect. Collectively, these results describe a position effect that downregulates TRPS1 expression as the probable cause of hypertrichosis in AS in humans and the Koa phenotype in mice.