Genetic and Molecular Basis of Cleft Lip and Palate: A Comprehensive Review.

Cleft lip and palate (CL/P) are among the most common congenital craniofacial anomalies, arising from disruptions in facial development during early embryogenesis. These conditions show significant clinical and genetic heterogeneity and are broadly classified into syndromic and nonsyndromic forms. The objective of this review is to summarize current knowledge on the embryological, genetic, and molecular mechanisms underlying CL/P and to highlight their clinical implications. A comprehensive review of the literature was conducted, focusing on studies in developmental biology, human genetics, and genomics related to CL/P. Emphasis was placed on both syndromic and nonsyndromic forms, including findings from genome-wide association studies, gene mutation analyses, and investigations of gene-environment interactions. Syndromic clefting is frequently associated with pathogenic variants in genes such as IRF6, TP63, and TBX22, which play key roles in epithelial differentiation, transcriptional regulation, and palatal development. In contrast, nonsyndromic CL/P results from complex interactions between multiple genetic variants and environmental factors. Genome-wide association studies have identified numerous susceptibility loci, many located in noncoding regulatory regions active during craniofacial development. Environmental influences, including maternal nutrition, smoking, alcohol exposure, and folate metabolism, have been shown to significantly modify risk. CL/P is a multifactorial condition involving intricate interactions between genetic and environmental factors. Advances in genomics and developmental biology have enhanced understanding of its etiology and are contributing to improved risk assessment, diagnosis, and the development of future precision medicine approaches.