Large Deletions at the SHOX Locus in the Pseudoautosomal Region Are Associated with Skeletal Atavism in Shetland Ponies
G3-GENES GENOMES GENETICS
Authors: Rafati, Nima; Andersson, Lisa S.; Mikko, Sofia; Feng, Chungang; Raudsepp, Terje; Pettersson, Jessica; Janecka, Jan; Wattle, Ove; Ameur, Adam; Thyreen, Gunilla; Eberth, John; Huddleston, John; Malig, Maika; Bailey, Ernest; Eichler, Evan E.; Dalin, Goran; Chowdary, Bhanu; Andersson, Leif; Lindgren, Gabriella; Rubin, Carl-Johan
Abstract
Skeletal atavism in Shetland ponies is a heritable disorder characterized by abnormal growth of the ulna and fibula that extend the carpal and tarsal joints, respectively. This causes abnormal skeletal structure and impaired movements, and affected foals are usually killed. In order to identify the causal mutation we subjected six confirmed Swedish cases and a DNA pool consisting of 21 control individuals to whole genome resequencing. We screened for polymorphisms where the cases and the control pool were fixed for opposite alleles and observed this signature for only 25 SNPs, most of which were scattered on genome assembly unassigned scaffolds. Read depth analysis at these loci revealed homozygosity or compound heterozygosity for two partially overlapping large deletions in the pseudoautosomal region (PAR) of chromosome X/Y in cases but not in the control pool. One of these deletions removes the entire coding region of the SHOX gene and both deletions remove parts of the CRLF2 gene located downstream of SHOX. The horse reference assembly of the PAR is highly fragmented, and in order to characterize this region we sequenced bacterial artificial chromosome (BAC) clones by single-molecule real-time (SMRT) sequencing technology. This considerably improved the assembly and enabled size estimations of the two deletions to 1602180 kb and 60280 kb, respectively. Complete association between the presence of these deletions and disease status was verified in eight other affected horses. The result of the present study is consistent with previous studies in humans showing crucial importance of SHOX for normal skeletal development.
Copy number alterations determined by single nucleotide polymorphism array testing in the clinical laboratory are indicative of gene fusions in pediatric cancer patients
GENES CHROMOSOMES & CANCER
Authors: Busse, Tracy M.; Roth, Jacquelyn J.; Wilmoth, Donna; Wainwright, Luanne; Tooke, Laura; Biegel, Jaclyn A.
Abstract
Gene fusions resulting from structural rearrangements are an established mechanism of tumorigenesis in pediatric cancer. In this clinical cohort, 1,350 single nucleotide polymorphism (SNP)based chromosomal microarrays from 1,211 pediatric cancer patients were evaluated for copy number alterations (CNAs) associated with gene fusions. Karyotype or fluorescence in situ hybridization studies were performed in 42% of the patients. Ten percent of the bone marrow or solid tumor specimens had SNP array-associated CNAs suggestive of a gene fusion. Alterations involving ETV6, ABL1-NUP214, EBF1-PDGFRB, KMT2A(MLL), LMO2-RAG, MYH11-CBFB, NSD1-NUP98, PBX1, STIL-TAL1, ZNF384-TCF3, P2RY8-CRLF2, and RUNX1T1-RUNX1 fusions were detected in the bone marrow samples. The most common alteration among the low-grade gliomas was a 7q34 tandem duplication resulting in a KIAA1549-BRAF fusion. Additional fusions identified in the pediatric brain tumors included FAM131B-BRAF and RAF1-QKI. COL1A1-PDGFB, CRTC1-MAML2, EWSR1, HEY1, PAX3-and PAX7-FOXO1, and PLAG1 fusions were determined in a variety of solid tumors and a novel potential gene fusion, FGFR1-USP6, was detected in an aneurysmal bone cyst. The identification of these gene fusions was instrumental in tumor diagnosis. In contrast to hematologic and solid tumors in adults that are predominantly driven by mutations, the majority of hematologic and solid tumors in children are characterized by CNAs and gene fusions. Chromosomal microarray analysis is therefore a robust platform to identify diagnostic and prognostic markers in the clinical setting.