STRs database » XYLT1 locus
Overview of repeats
Desbuquois dysplasia-2 (DBQD2), also known as the Baratela-Scott syndrome is caused by mutations in the XYLT1 gene and LaCroix et al. (2019) discovered that GGC repeat expansions in the XYLT1 can be disease-causing as well. By investigating 12 individuals from 10 families with DBQD2, a 238 bp sequence missing from the reference genome (hg19 and hg38) was discovered. In that sequence, expanded, hypermethylated alleles estimated at approximately 110-850 repeats were identified in affected individuals from eight of the ten families. The 238 bp sequence was seen to be present in the control group (100 individuals) as well, where GGC repeats were in the range of 9-20 repeats (LaCroix et al. (2019)). The authors noted that up to 72 repeats had previously been observed on chromosomes without the fragile site and placed the minimum size associated with hypermethylation between 216 bp and approximately 360 bp, rather than establishing 72 as pathogenic. Miller et al. (2021) subsequently demonstrated partial methylation of a maternal premutation haplotype in follow-up of the discovery families.
NB! The repeated region is not in the hg38 and hg19 reference genome, but the locus can be genotyped by STRipy or with XYLT1 STR caller that is realigning a sample onto a genome containing the 238 bp reference-missing sequence.