The role of the TCF4 gene in the phenotype of individuals with 18q segmental deletions

The goal of this study is to define the effects of TCF4 hemizygosity in the context of a larger segmental deletion of chromosome 18q. Our cohort included 37 individuals with deletions of 18q. Twenty-seven had deletions including TCF4 (TCF4 ^+/-); nine had deletions that did not include TCF4 (TCF4 ^+/+); and one individual had a microdeletion that included only the TCF4 gene. We compared phenotypic data from the participants' medical records, survey responses, and in-person evaluations. Features unique to the TCF4 ^+/- individuals included abnormal corpus callosum, short neck, small penis, accessory and wide-spaced nipples, broad or clubbed fingers, and sacral dimple. The developmental data revealed that TCF4 ^+/+ individuals were only moderately developmentally delayed while TCF4 ^+/- individuals failed to reach developmental milestones beyond those typically acquired by 12 months of age. TCF4 hemizygosity also conferred an increased risk of early death principally due to aspiration-related complications. Hemizygosity for TCF4 confers a significant impact primarily with regard to cognitive and motor development, resulting in a very different prognosis for individuals hemizygous for TCF4 when compared to individuals hemizygous for other regions of distal 18q.