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Characterization of novel genes insolved in non syndromic cleft lip with or with out cleft palate (NSCLP)
Bianco, Anna Monica Rosaria
2010-04-19
Abstract
Non-syndromic cleft lip with or without cleft palate (NSCLP) is one of the most common birth defect. Genetic studies on human populations have identified numerous predisposing factors, as MYH9 and JARID2, whose role during palatogenesis remains obscure. In order to improve our knowledge on pathogenetic mechanisms, we carried out expression studies during mouse palate development using RNA in situ hybridization. As reference genes (Tgfb3, Irf6, Pvrl1, Foxe1 and Tp63) known to be required for correct palate formation, Jarid2 and Myh9 are expressed in the epithelial cells of the palatine processes before and at the time of contact. Then, this signal decreases and eventually disappears concomitantly with the degradation of the medial epithelial cells. Consistent with these observations, RT-PCR carried out on dissected palatal shelves detected products of Myh9 and Jarid2 from embryonic day E14.0 to E15.0 with a pick at E14.5, the stage when shelves appose in the midline. Taken together, these expression studies strongly support the association studies that designate these genes as predisposing factors for NSCLP.
In multifactorial diseases as NSCLP once genetic studies demonstrate association, a major challenge is to identify mutations. In this regard, we started analyzing two in linkage disequilibrium SNPs (rs3752462 of MYH9 and rs2076056 of JARID2) that could be involved in defective splicing mechanisms, as hypothesized on the basis of their localization within splice sites. Using a hybrid minigene assay, however, we demonstrated that none of the allelic variants lead to any aberrant products at least in HeLa cells, the model used for this study.
Moreover, we investigated whether alternative splicing events of the Myh9 gene detected in cochlea and brain (Li et al., 2008) could also be found in other tissues and palate. A small insertion of 12 bp between exon 4 and 5 (loop1) due to an alternative splicing was detected in all adult tissues analyzed. The same insertion was not detected in embryonic tissues, such as palatal samples at different stages of development, and brain. These results suggest that the genomic region of loop1 should be investigated in all risk haplotypes to search for pathogenetic variants. In conclusion, further investigations should be planned to explore the role of MYH9 and JARID2 in orofacial development in order to dissect signaling pathways during palate formation and identify the causative variants contributing to NSCLP.
Insegnamento
Publisher
Università degli studi di Trieste
Languages
en
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