Loss of CHSY1, a secreted FRINGE enzyme, causes syndromic brachydactyly in humans via increased NOTCH signaling.
We delineated a syndromic recessive preaxial brachydactyly with partial duplication of proximal phalanges to 16.8 Mb over 4 chromosomes. High-throughput sequencing of all 177 candidate genes detected a truncating frameshift mutation in the gene CHSY1 encoding a chondroitin synthase with a Fringe domain. CHSY1 was secreted from patients' fibroblasts and was required for synthesis of chondroitin sulfate moieties. Noticeably, its absence triggered massive production of JAG1 and subsequent NOTCH activation, which could only be reversed with a wild-type but not a Fringe catalytically dead CHSY1 construct. In vitro, depletion of CHSY1 by RNAi knockdown resulted in enhanced osteogenesis in fetal osteoblasts and remarkable upregulation of JAG2 in glioblastoma cells. In vivo, chsy1 knockdown in zebrafish embryos partially phenocopied the human disorder; it increased NOTCH output and impaired skeletal, pectoral-fin, and retinal development. We conclude that CHSY1 is a secreted FRINGE enzyme required for adjustment of NOTCH signaling throughout human and fish embryogenesis and particularly during limb patterning.
Institute of Medical Biology, A(∗)STAR, Singapore.
Jing
J
Tian
Ling
L
Ling
Mohammad
M
Shboul
Hane
H
Lee
Brian
B
O'Connor
Barry
B
Merriman
Stanley F
SF
Nelson
Simon
S
Cool
Osama H
OH
Ababneh
Azmy
A
Al-Hadidy
Amira
A
Masri
Hanan
H
Hamamy
Bruno
B
Reversade
D000595:Amino Acid Sequence; D002478:Cells, Cultured; D005260:Female; D005532:Foot Deformities, Congenital / Q000235:genetics*; D016368:Frameshift Mutation; D005838:Genotype; D006228:Hand Deformities, Congenital / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000737:chemistry / Q000235:genetics*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D051880:Receptors, Notch / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013577:Syndrome
D051880:Receptors, Notch; D017350:N-Acetylgalactosaminyltransferases; C412725:chondroitin synthase