Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes

Abstract

Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit. Since the characteristics of these syndromes overlap, it has been argued whether they are distinct entities or different manifestations of a single syndrome. Several mutations causing Stickler syndrome have been found in the COL2A1 gene, and one mutation causing Stickler syndrome and one causing Marshall syndrome have been detected in the COL11A1 gene. We characterize here the genomic structure of the COL11A1 gene. Screening of patients with Stickler, Stickler-like, or Marshall syndrome pointed to 23 novel mutations. Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene. Null-allele mutations in the COL2A1 gene led to a typical phenotype of Stickler syndrome. Some patients, however, presented with phenotypes of both Marshall and Stickler syndromes.

Figure 1

Schematic presentation of the genomic organization of the COL11A1 gene and the genomic clones covering the gene, drawn to scale. The clone addresses are BACH-86N5 (1), DMPC-HFF#1-140(B10) (2), PAC-154-1M (3), PAC 84:8A (4), and 170O21 (5).

Figure 2

Facial features of patient 16 (A and B), clinically diagnosed with Stickler syndrome, and patients 7 (C and D) and 6 (E and F), clinically diagnosed with Marshall syndrome.