PERCC1, a new member of the Yap/TAZ/FAM181 transcriptional co-regulator family

Nonsense mutation in the novel PERCC1 gene as a genetic cause of congenital diarrhea and enteropathy

Congenital diarrheas and enteropathies (CODEs) constitute a heterogeneous group of individually rare disorders manifesting with infantile-onset chronic diarrhea. Genomic deletions in chromosome 16, encompassing a sequence termed the 'intestine-critical region (ICR)', were recently identified as the cause of an autosomal recessive congenital enteropathy. The regulatory sequence within the ICR is flanked by an unannotated open reading frame termed PERCC1, which plays a role in enteroendocrine cell (EEC) function. We investigated two unrelated children with idiopathic congenital diarrhea requiring home parenteral nutrition attending the Irish Intestinal Failure Program. Currently 12 and 19-years old, these Irish male patients presented with watery diarrhea and hypernatremic dehydration in infancy. Probands were phenotyped by comprehensive clinical investigations, including endoscopic biopsies and serum gastrin level measurements. Following negative exome sequencing, PCR and Sanger sequencing of the entire coding region and intron boundaries of PERCC1 were performed for each proband and their parents. In both patients, serum gastrin levels were low and failed to increase following a meal challenge. While no deletions involving the ICR were detected, targeted sequencing of the PERCC1 gene revealed a shared homozygous c.390C > G stop gain variant. We report clinical and molecular findings in two unrelated patients harboring a shared homozygous variant in PERCC1, comprising the first description of a point mutation in this gene in association with CODE. That both parenteral nutrition dependent children with unexplained diarrhea at our institution harbored a PERCC1 mutation underscores the importance of its inclusion in exome sequencing interpretation.

The genetics of monogenic intestinal epithelial disorders

Monogenic intestinal epithelial disorders, also known as congenital diarrheas and enteropathies (CoDEs), are a group of rare diseases that result from mutations in genes that primarily affect intestinal epithelial cell function. Patients with CoDE disorders generally present with infantile-onset diarrhea and poor growth, and often require intensive fluid and nutritional management. CoDE disorders can be classified into several categories that relate to broad areas of epithelial function, structure, and development. The advent of accessible and low-cost genetic sequencing has accelerated discovery in the field with over 45 different genes now associated with CoDE disorders. Despite this increasing knowledge in the causal genetics of disease, the underlying cellular pathophysiology remains incompletely understood for many disorders. Consequently, clinical management options for CoDE disorders are currently limited and there is an urgent need for new and disorder-specific therapies. In this review, we provide a general overview of CoDE disorders, including a historical perspective of the field and relationship to other monogenic disorders of the intestine. We describe the genetics, clinical presentation, and known pathophysiology for specific disorders. Lastly, we describe the major challenges relating to CoDE disorders, briefly outline key areas that need further study, and provide a perspective on the future genetic and therapeutic landscape.