Heterozygous truncating variants in SUFU cause congenital ocular motor apraxia

Authors

Schröder S, Li Y, Yigit G, Altmüller J, Bader I, Bevot A, Biskup S, Dreha-Kulaczewski S, Christoph Korenke G, Kottke R, Mayr JA, Preisel M, Toelle SP, Wente-Schulz S, Wortmann SB, Hahn H, Boltshauser E, Uhmann A, Wollnik B, Brockmann K

Journal

Genetics in Medicine

Citation

Genet Med. 2020 Oct 7.

Abstract

Purpose
This study aimed to delineate the genetic basis of congenital ocular motor apraxia (COMA) in patients not otherwise classifiable.
Methods
We compiled clinical and neuroimaging data of individuals from six unrelated families with distinct clinical features of COMA who do not share common diagnostic characteristics of Joubert syndrome or other known genetic conditions associated with COMA. We used exome sequencing to identify pathogenic variants and functional studies in patient-derived fibroblasts.
Results
In 15 individuals, we detected familial as well as de novo heterozygous truncating causative variants in the Suppressor of Fused (SUFU) gene, a negative regulator of the Hedgehog (HH) signaling pathway. Functional studies showed no differences in cilia occurrence, morphology, or localization of ciliary proteins, such as smoothened. However, analysis of expression of HH signaling target genes detected a significant increase in the general signaling activity in COMA patient–derived fibroblasts compared with control cells. We observed higher basal HH signaling activity resulting in increased basal expression levels of GLI1, GLI2, GLI3, and Patched1. Neuroimaging revealed subtle cerebellar changes, but no full-blown molar tooth sign.
Conclusion
Taken together, our data imply that the clinical phenotype associated with heterozygous truncating germline variants in SUFU is a forme fruste of Joubert syndrome.

DOI

10.1038/s41436-020-00979-w
 
Pubmed Link