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Functional analysis of natural mutations in two TWIST protein motifs
Author(s) -
Funato Noriko,
Twigg Stephen R.F.,
Higashihori Norihisa,
Ohyama Kimie,
Wall Steven A.,
Wilkie Andrew O.M.,
Nakamura Masataka
Publication year - 2005
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.20176
Subject(s) - biology , twist , genetics , computational biology , natural (archaeology) , paleontology , geometry , mathematics
The basic helix‐loop‐helix protein Twist, a transcriptional repressor, is essential for embryogenesis in both invertebrates and vertebrates. Haploinsufficiency of the human TWIST1 gene, which causes the craniosynostosis disorder Saethre‐Chotzen syndrome (SCS), is related to failure to repress transcription of CDKN1A (which encodes p21/WAF1/CIP1), promoting osteoblast differentiation. We have examined the functional significance of natural TWIST1 variants present in craniosynostosis patients and in their healthy relatives. Both deletion and duplication variants of the glycine‐rich tract Gly 5 AlaGly 5 inhibited E2A (E12/E47)‐dependent transcription of CDKN1A to a similar degree as wild‐type protein, indicating that the length of this glycine tract is not critical for efficient transcriptional repression. We also evaluated a newly identified heterozygous TWIST1 variant (c.115C>G, encoding p.Arg39Gly), located within a putative nuclear localization signal (NLS), that was present in a child with mild SCS and her clinically unaffected father and grandmother. Unlike wild‐type protein, this mutant required cotransfected E12 to localize to the nucleus, indicating that the NLS, including amino acid 39, is essential for nuclear localization; inhibition of E2A‐dependent transcription of CDKN1A occurred normally. This analysis further dissects the structure‐function relationships of TWIST and corroborates with phenotypic observations of disease expressivity. Hum Mutat 25:550–556, 2005. © 2005 Wiley‐Liss, Inc.