Deletions of the FOXP1 gene determine clinical manifestations in patients with chromosome 3p13 deletion

Meerschaut I, Rochefort D, Revençu N, et al. “FOXP1-related intellectual disability syndrome: a recognisable entity”. J. Med. Genet. 2017, v. 54, 613-623.

Patients with proximal short arm deletions of chromosome 3 (3p13) show intellectual disability (ID), speech and language issues, neurodevelopmental delay, spasticity (increased muscle tone), contractures (shortening and hardening of muscles), mild structural brain abnormalities, and epilepsy. Some of them also have ocular, cardiovascular, and genitourinary abnormalities. Dysmorphic features have also been observed, which include macrocephaly (abnormally large head), a wide forehead, ptosis (drooping of the upper eyelid), a wide mouth with downturned corners, and full, red lips. Behavioral disorders – including autism, hyperactivity, aggression, mood lability, and obsessive-compulsive disorder – occurred in some patients, but not all.

This area of 3p13 contains several genes. One of these genes FOXP1 encodes a protein called forkhead box protein P1. This gene is widely expressed throughout the body, and is thought to be involved in the development of many organ systems.

The authors describe 6 “new” patients having 3-6 Mb deletions in this area and 19 patients with point mutations of the FOXP1 gene. They compared this data with 20-30 previously reported patients with deletions involving FOXP1 and mutations of this gene. The analysis showed that patients with deletions and point mutations have virtually the same spectrum and the same incidence of abnormalities. This allowed the conclusion that the FOXP1 gene is the main gene responsible for the clinical characteristics of patients with deletions of chromosome 3p13 involving the FOXP1 gene.

The article concludes with information on treatment options for those with the FOXP1 deletions and mutations. Patients with the FOXP1 deletion should first be screened for additional organ system issues, since this gene is expressed throughout the body. This includes a detailed clinical examination, eye and hearing evaluations, echocardiograms, and an ultrasound of the genitourinary tract. If the patient has epilepsy, then a brain MRI should also be considered. Physiotherapy should be considered in those with chronic spasticity.