Different mutations in TBL1XR1 lead to diverse phenotypes of neurodevelopmental disorder: two case reports

The TBL1XR1 gene (Transducin beta-like 1X-linked receptor 1) is responsible for encoding the TBL1XR1 protein, an important component of the NCoR and SMRT corepressor complexes. 48 missense variants of the TBL1XR1 gene have been reported, which are associated with various phenotypes of neurodevelopmental disorders, including West syndrome, Pierpont syndrome, and others. However, given the important role of TBL1XR1 in neurological diseases, it is still necessary to further explore the variation of TBL1XR1. In this study, we present two patients with distinct variants and phenotypes. Patient 1 exhibits global developmental delay, intellectual disability, delayed language development, and seizures. While patient 2 displays mild facial dysmorphism, significant developmental delay, feeding difficulties, and increased muscle tone. Through trio whole-exome sequencing, two novel pathogenic variants in the TBL1XR1 gene were identified: A heterozygous NM_024665.6:c.940G > T (p.Val314Phe) variant in patient 1 and a heterozygous NM_024665.6:c.1387G > T (p.Asp463Tyr) in patient 2. Discovery of these two novel variant sites expands the mutation spectrum associated with the TBL1XR1 gene.