Functional analysis of TCF4 missense mutations that cause Pitt-Hopkins syndrome.

Pitt-Hopkins syndrome (PTHS) is a rare developmental disorder associated with severe mental retardation, facial abnormalities, and intermittent hyperventilation. Autosomal dominant PTHS is caused by mutations in the transcription factor 4 (TCF4) gene, whereas NRXN1 and CNTNAP2 mutations are associated with autosomal recessive PTHS. To determine the impact of missense mutations on TCF4 function, we tested a panel of PTHS-associated mutations using a range of quantitative techniques. Mutations in the basic helix-loop-helix (bHLH) domain of TCF4 alter the subnuclear localization of the mutant protein and can attenuate homo- and heterodimer formation in homogenous time-resolved fluorescence (HTRF) assays. By contrast, mutations proximal to the bHLH domain do not alter the location of TCF4 or impair heterodimer formation. In addition, we show that TCF4 can transactivate the NRXN1β and CNTNAP2 promoters in luciferase assays. Here we find variable, context-specific deficits in the ability of the different PTHS-associated TCF4 mutants to transactivate these promoters when coexpressed with different bHLH transcription factors. These data demonstrate that PTHS-associated missense mutations can have multiple effects on the function of the protein, and suggest that TCF4 may modulate the expression of NRXN1 and CNTNAP2 thereby defining a regulatory network in PTHS.

Forrest M ，Chapman RM ，Doyle AM ，Tinsley CL ，Waite A ，Blake DJ ... -  《-》

Pitt-Hopkins syndrome-associated mutations in TCF4 lead to variable impairment of the transcription factor function ranging from hypomorphic to dominant-negative effects.

Sepp M ，Pruunsild P ，Timmusk T 《-》

Novel comprehensive diagnostic strategy in Pitt-Hopkins syndrome: clinical score and further delineation of the TCF4 mutational spectrum.

Pitt-Hopkins syndrome (PTHS), characterized by severe intellectual disability and typical facial gestalt, is part of the clinical spectrum of Rett-like syndromes. TCF4, encoding a basic helix-loop-helix (bHLH) transcription factor, was identified as the disease-causing gene with de novo molecular defects. While PTHS appears to be a recognizable clinical entity, it seems to remain underdiagnosed, especially when facial gestalt is less typical. With the aim to facilitate the diagnosis of PTHS and to increase its rate and specificity, we have investigated 33 novel patients and defined a Clinical Diagnosis Score. Analysis of 112 individuals (79 previously reported and 33 novel patients) allowed us to delineate the TCF4 mutational spectrum, with 40% point mutations, 30% small deletions/insertions, and 30% deletions. Most of these were private mutations and generated premature stop codons. Missense mutations were localized in the bHLH domain, which is a mutational hotspot. No obvious difference was observed between patients harboring truncating, missense mutations, or deletions, further supporting TCF4 haploinsufficiency as the molecular mechanism underlying PTHS. In this study, we have summarized the current knowledge of TCF4 molecular pathology, reported all the mutations in the TCF4 database (http://www.LOVD.nl/TCF4), and present a novel and comprehensive diagnostic strategy for PTHS.

Whalen S ，Héron D ，Gaillon T ，Moldovan O ，Rossi M ，Devillard F ，Giuliano F ，Soares G ，Mathieu-Dramard M ，Afenjar A ，Charles P ，Mignot C ，Burglen L ，Van Maldergem L ，Piard J ，Aftimos S ，Mancini G ，Dias P ，Philip N ，Goldenberg A ，Le Merrer M ，Rio M ，Josifova D ，Van Hagen JM ，Lacombe D ，Edery P ，Dupuis-Girod S ，Putoux A ，Sanlaville D ，Fischer R ，Drévillon L ，Briand-Suleau A ，Metay C ，Goossens M ，Amiel J ，Jacquette A ，Giurgea I ... -  《-》

Two percent of patients suspected of having Angelman syndrome have TCF4 mutations.

Takano K ，Lyons M ，Moyes C ，Jones J ，Schwartz CE ... -  《-》

A case of Pitt-Hopkins syndrome with absence of hyperventilation.

Inati A ，Abbas HA ，Korjian S ，Daaboul Y ，Harajeily M ，Saab R ... -  《-》