title: A missense T (Brachyury) mutation contributes to vertebral malformations.
abstract: No major susceptibility genes for sporadically occurring congenital vertebral malformations (CVM) in humans have been identified to date. Body patterning genes whose mutants cause axial skeletal anomalies in mice are candidates for human CVM susceptibility. T (also known as Brachyury) and TBX6 are critical genes needed to establish mesodermal identity. We hypothesized that mutations in T and/or TBX6 contribute to the pathogenesis of human CVMs. The complete T and TBX6 coding regions, splice junctions, and proximal 500 bp of the promoters were sequenced in 50 phenotyped patients with CVM. Three unrelated patients with sacral agenesis, Klippel-Feil syndrome, and multiple cervical and thoracic vertebral malformations were heterozygous for a c.1013C>T substitution, resulting in a predicted Ala338Val missense alteration in exon 8. A clinically unaffected parent of each patient also harbored the substitution, but the variant did not occur in an ethnically diverse, 443-person reference population. The c.1013C>T variant is significantly associated with CVM (p < 0.001). Alanine 338 shows moderate conservation across species, and valine at this position has not been reported in any species. A fourth patient harbored a c.908-8C>T variant in intron 7. This previously unreported variant was tested in 347 normal control subjects, and 11 heterozygotes and 2 T/T individuals were found. No TBX6 variants were identified. We infer that the c.1013C>T substitution is pathogenic and represents the first report of an association between a missense mutation in the T gene and the occurrence of sporadic CVMs in humans. It is uncertain whether the splice junction variant increases CVM risk. TBX6 mutations do not seem to be associated with CVM. We hypothesize that epistatic interactions between T and other developmental genes and the environment modulate the phenotypic consequences of T variants.
authors.affiliation: Molecular Diagnostic Research Laboratory, Marshfield Clinic, Marshfield, Wisconsin 54449, USA.
authors.forename: Nader
authors.initials: N
authors.lastname: Ghebranious
authors.forename: Robert D
authors.initials: RD
authors.lastname: Blank
authors.forename: Cathleen L
authors.initials: CL
authors.lastname: Raggio
authors.forename: Justin
authors.initials: J
authors.lastname: Staubli
authors.forename: Elizabeth
authors.initials: E
authors.lastname: McPherson
authors.forename: Lynn
authors.initials: L
authors.lastname: Ivacic
authors.forename: Kristen
authors.initials: K
authors.lastname: Rasmussen
authors.forename: F Stig
authors.initials: FS
authors.lastname: Jacobsen
authors.forename: Thomas
authors.initials: T
authors.lastname: Faciszewski
authors.forename: James K
authors.initials: JK
authors.lastname: Burmester
authors.forename: Richard M
authors.initials: RM
authors.lastname: Pauli
authors.forename: Oheneba
authors.initials: O
authors.lastname: Boachie-Adjei
authors.forename: Ingrid
authors.initials: I
authors.lastname: Glurich
authors.forename: Philip F
authors.initials: PF
authors.lastname: Giampietro
mesh_terms: D000328:Adult; D001483:Base Sequence; D002648:Child; D015331:Cohort Studies; D017931:DNA Primers; D005326:Fetal Proteins / Q000235:genetics*; D006801:Humans; D020125:Mutation, Missense; D011859:Radiography; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013131:Spine / Q000002:abnormalities* / Q000000981:diagnostic imaging; D020825:T-Box Domain Proteins / Q000235:genetics*; D000098908:Brachyury Protein
chemical_list: D017931:DNA Primers; D005326:Fetal Proteins; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein