Focal Adhesion Kinase Variants May Contribute to Risk of Human Myelomeningocele

Myelomeningocele (MMC) is the most severe form of an open neural tube defect (NTD) that is compatible with life. The prevalence of MMC in the United States is 1 in 2,500 live births, with the two ethnicities that have the highest occurrence of MMC being Mexican American (MA) and Caucasian American (EA). Research to date has shown that MMC results from a cumulative effect of environmental and genetic factors. Therefore, determining the underlying molecular etiology would be a step toward developing strategies for prevention and treatment. We examined variants in 568 nervous system development genes implicated in MMC by whole exome sequencing of 254 MA and 257 EA subjects born with MMC. Mutational burden analysis was used to compare the deleterious variant load between MMC subjects and the reference population in the Genome Aggregation Exome Database (gnomADe). Higher mutational burdens were found in 18 genes, with PTK2 being the most significant (OR=3.49, p=5.3e-3) among genes known to be expressed in the human neural tube at the CS12/CS13 stages. Cell migration assay was performed using seven PTK2 (aka FAK1) deleterious variants in transfected Fak-/- mouse embryonic cells. The effect of Ptk2 knockdown on neural tube development was examined using Xenopus embryos. Cell migration assay results showed the seven MMC-associated PTK2 variants significantly affected migratory capacity compared to the wild-type PTK2. The Knockdown of Ptk2 significantly affected the normal neural tube closure of Xenopus embryos. Based on these findings, PTK2 variants identified from MMC patients may play a role in the multifactorial causation of MMC.