Dissection of the Genetic and Molecular Pathways of Cleft Lip and Palate

Abstract

Cleft lip and palate (CLP) is a congenital anomaly affecting the lips and oral cavity and known to have an impact on the quality of life of the individuals who have it. This disease is known to be caused by both environmental and genetic factors and its etiology has been widely studied over the years but is still not close to being fully deciphered. Using whole exome sequencing (WES), we have identified in a Lebanese family two novel CLP variants in two different integrin subtypes coding for ITGA10 and ITGB8 genes. Integrins are cell surface proteins consisting of several subtypes and act as an interface between the extra cellular matrix (ECM) and internal cell signaling pathways involved in many cellular processes such as migration and differentiation (Integrins - an Overview | ScienceDirect Topics, n.d.). In order to further validate our findings, functional tests have been conducted on primary gingival fibroblasts collected from an affected individual of the studied family. Gene and protein expression analysis showed a differential expression of the identified mutated integrins. Cells’ viability, adhesion and motility were studied to be able to identify the process being altered in the affected cells. The cells collected from the proband appeared to have increased adhesion to the ECM and an overall decrease in its motility when compared to wild type gingival fibroblasts used as a control. This deficit in the cells’ migratory ability was attributed to a decrease in the activity of Ras-related C3 botulinum toxin substrate 1 (Rac1), a member of the Rac family of small GTPases known to play role in cytoskeletal reorganization of the cell and ultimately its motility. This study contributes to the process of establishing of a genotype-phenotype correlation in CLP that helps in better understanding the etiology of this complex disease. It does so by emphasizing the role of cell motility in lip and palate formation and establishing one of the mechanisms by which this function can be altered.