Non-Coding c.*6C>T Variant in RBM8A Associated With Thrombocytopenia-Absent Radius (TAR) Syndrome in Three Indian Patients.

Thrombocytopenia-absent radius (TAR) syndrome is a rare genetic disorder characterized by the absence of radius in the forearms and a decrease in platelet count. The molecular basis of TAR syndrome is linked to a heterozygous minimal deletion within the 1q21.1 region spanning 200 k bases (kb), resulting in a null allele and a nucleotide variation in RBM8A resulting in a hypomorphic allele. Previous studies have identified pathogenic variants in the coding regions of the RBM8A gene as the cause of TAR syndrome. However, the involvement of non-coding variants in disease pathogenesis remains largely unexplored. We investigated the association of a non-coding 3' UTR variant, c.*6C>T, in RBM8A with TAR syndrome in three individuals from two unrelated families of Indian origin. Our study provides evidence that this variant is associated with decreased stability of the transcript and is a hypomorphic allele with disease-causing impact when in trans with a null allele (1q21.1 deletion). The present work is the first application of an mRNA stability assay to directly detect RNA degradation in patients with non-coding RBM8A variants causing TAR syndrome.