Identification of Variants in the 4q35 Gene FAT1 in Patients with a Facioscapulohumeral Dystrophy-Like Phenotype

Francesca Puppo (1) , Eugénie Dionnet (1) , Marie-Cécile Gaillard (1) , Pascaline Gaildrat (2) , Christel Castro (1) , Catherine Vovan (3) , Karine Bertaux (3, 1) , Rafaelle Bernard (3, 1) , Shahram Attarian (1, 4) , Kanako Goto , Ichizo Nishino , Yukiko Hayashi , Frédérique Magdinier (1) , Martin Krahn (1) , Françoise Helmbacher (5) , Marc Bartoli (1) , Nicolas Lévy (3, 1)

1 GMGF - Génétique Médicale et Génomique Fonctionnelle
2 Génétique médicale et fonctionnelle du cancer et des maladies neuropsychiatriques
3 Département de génétique médicale [Hôpital de la Timone - APHM]
4 Centre de référence des maladies neuromusculaires et de la SLA
5 IBDM - Institut de Biologie du Développement de Marseille

Facioscapulohumeralmuscular dystrophy (FSHD) is linked to copy-number reduction (N < 10) of the 4q D4Z4 subtelomeric array, in association with DUX4-permissive haplo-types. This main form is indicated as FSHD1. FSHD-like phenotypes may also appear in the absence of D4Z4 copy-number reduction. Variants of the SMCHD1 gene have been reported to associate with D4Z4 hypomethylation in DUX4-compatible hap-lotypes, thus defining FSHD2. Recently, mice carrying a muscle-specific knockout of the protocadherin gene Fat1 or its consti-tutive hypomorphic allele were shown to develop muscular and nonmuscular defects mimicking human FSHD. Here, we report FAT1 variants in a group of patients presenting with neuro-muscular symptoms reminiscent of FSHD. The patients do not carry D4Z4 copy-number reduction, 4q hypomethylation, or SM-CHD1 variants. However, abnormal splicing of the FAT1 transcript is predicted for all identified variants. To determine their pathogenicity, we elaborated a minigene approach coupled to an antisense oligonucleotide (AON) assay. In vitro, four out of five selected variants induced partial or complete alteration of splicing by creating new splice sites or modifying splicing regulators. AONs confirmed these effects. Altered transcripts may affect FAT1 protein interactions or stability. Altogether, our data suggest that defective FAT1 is associated with an FSHD-like phenotype. Hum Mutat 36:443–453, 2015. C 2015 Wiley Periodicals, Inc.

Mots clés: neuromuscular pathology; facioscapulo- humeral dystrophy; FAT1-protocadherin

Domaines: Génétique humaine; Biologie cellulaire

Francesca Puppo, Eugénie Dionnet, Marie-Cécile Gaillard, Pascaline Gaildrat, Christel Castro, et al.. Identification of Variants in the 4q35 Gene FAT1 in Patients with a Facioscapulohumeral Dystrophy-Like Phenotype. Human Mutation, 2015, 36 (4), pp.443 - 453. ⟨10.1002/humu.22760⟩. ⟨hal-01662841⟩