The Association of TOX3 Copy Number Variation with Gene Expression and Susceptibility to Nonsyndromic Cleft Lip and/or Palate in a Malay Cohort Nonsyndromic cleft lip and/or palate (NSCL/P) is a common congenital malformation with genetic influences. While Thymocyte selection-associated high mobility group box 3 (TOX3) is involved in other developmental processes, its role in NSCL/P remained unexplored. This study investigated the association between TOX3 copy number, expression, and NSCL/P in 64 Malay NSCL/P cases and 64 normal controls. Samples from patients undergoing cleft repair surgery and eligible volunteers for the control group were quantified via quantitative polymerase chain reactions (qPCR). A higher mean of TOX3 copy number was found in cases (2.195 ± 0.689) compared to controls (1.962 ± 0.558; p < 0.05). Similarly, a higher TOX3 expression was observed in cases (0.014 [IQR 0.024]) compared to controls (0.006 [IQR 0.019]; p < 0.001). Unadjusted analyses showed higher TOX3 copy number (OR = 1.850; p < 0.05) and its expression associated with NSCL/P. However, these associations were nullified after adjusting for sex and age (p > 0.05). Instead, male sex emerged as a significant independent predictor for NSCL/P (adjusted OR = 4.03; p < 0.001). Besides, an inverse, weak correlation was observed between TOX3 copy number and expression in NSCL/P patients (ρ = –0.285; p < 0.05) indicating the potential role of epigenetics in this condition. While male sex strongly contributed to the NSCL/P condition, our results suggest that TOX3 is not an independent genetic risk factor for NSCL/P in this population. These results highlight sex as a primary demographic risk factor and underscore the importance of considering demographic context in genetic association studies.

ABSTRACT Orofacial clefts (OFC) are one of the most common birth defects that affects the lip, palate, or lip and palate of an infant. The deterioration of clefts is multifactorial involving multiple genes, various interactions from environmental factor and most forgotten, mitochondrial abnormality. The aim of this review is to highlight the importance of mitochondrial activity related to non-syndromic OFC deformity. Despite its important role in cells, the study on mitochondrial activity in cleft pathology was scarce and almost forgotten compared to other genetic investigations. This systematic review was completed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The literature search was done via the following databases: Google Scholar, Pubmed and Scopus with a total of nine studies of mitochondrial abnormalities were included. We hypothesise that mitochondria play an important role in early craniofacial development. A decreased in its function or activity may result in cleft lip formation. Hence, we would like to shed light on the remarkable role of mitochondria activity in the pathogenesis of non-syndromic OFC.
Mitochondria--pathology ; DNA, Mitochondrial ; Cleft Lip ; Cleft Palate