Missense mutations in the homeodomain of HOXD13 are associated with brachydactyly types D and E.
HOXD13, the most 5' gene of the HOXD cluster, encodes a homeodomain transcription factor with important functions in limb patterning and growth. Heterozygous mutations of human HOXD13, encoding polyalanine expansions or frameshifts, are believed to act by dominant negative or haploinsufficiency mechanisms and are predominantly associated with synpolydactyly phenotypes. Here, we describe two mutations of HOXD13 (923C-->G encoding Ser308Cys and 940A-->C encoding Ile314Leu) that cause missense substitutions within the homeodomain. Both are associated with distinctive limb phenotypes in which brachydactyly of specific metacarpals, metatarsals, and phalangeal bones is the most constant feature, exhibiting overlap with brachydactyly types D and E. We investigated the binding of synthetic mutant proteins to double-stranded DNA targets in vitro. No consistent differences were found for the Ser308Cys mutation compared with the wild type, but the Ile314Leu mutation (which resides at the 47th position of the homeodomain) exhibited increased affinity for a target containing the core recognition sequence 5'-TTAC-3' but decreased affinity for a 5'-TTAT-3' target. Molecular modeling of the Ile314Leu mutation indicates that this mixed gain and loss of affinity may be accounted for by the relative positions of methyl groups in the amino acid side chain and target base.
Johnson
David
D
Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, and Department of Plastic and Reconstructive Surgery, Radcliffe Infirmary, Oxford, United Kingdom.
Kan
Shih-Hsin
SH
Oldridge
Michael
M
Trembath
Richard C
RC
Roche
Philippe
P
Esnouf
Robert M
RM
Giele
Henk
H
Wilkie
Andrew O M
AO
D000595:Amino Acid Sequence; D001132:Arm / Q000002:abnormalities; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D005260:Female; D005385:Fingers / Q000002:abnormalities*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007866:Leg / Q000002:abnormalities; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013580:Synostosis / Q000145:classification* / Q000235:genetics*; D014157:Transcription Factors
D017931:DNA Primers; C513184:HOXD13 protein, human; D018398:Homeodomain Proteins; D014157:Transcription Factors