Involvement of Tumor Suppressor Candidate 3 in Mouse Survival, Craniofacial, and Cortical Development

Tumor Suppressor Candidate 3 (TUSC3) is an integral component of the oligosaccharyltransferase complex and is required for the N-glycosylation of proteins. While TUSC3 has been implicated in cancer and autosomal recessive non-syndromic intellectual disability, some patients also exhibit distinct facial features. However, the role of Tusc3 in craniofacial development is unknown. Here, we report a patient presenting with cleft lip and palate who was found to carry a homozygous variant in the TUSC3 promoter region in addition to a maternally inherited chromosomal duplication. In order to evaluate a potential role for TUSC3 in craniofacial development, we analyzed Tusc3 deletion mouse mutants from the International Mouse Phenotyping Consortium (IMPC). Initial IMPC phenotyping data suggested that a subset of Tusc3 deletion mice could develop cleft palate, micrognathia, and aglossia. We further identified that Tusc3 is expressed in the craniofacial and brain regions during embryonic development. Upon characterizing the Tusc3 deletion line, we observed that most homozygous mutants exhibit preweaning lethality. While craniofacial defects occur at a very low frequency in the deletion mutants, we identified a consistent reduction in cortical area. Furthermore, RNA-seq analysis surprisingly revealed that no other genes in the developing brain or face were significantly affected upon loss of Tusc3. These findings suggest that Tusc3 can contribute to congenital malformations in both craniofacial and cortical development.