title: Haploinsufficiency of MSX1: a mechanism for selective tooth agenesis.
abstract: Previously, we found that the cause of autosomal dominant selective tooth agenesis in one family is a missense mutation resulting in an arginine-to-proline substitution in the homeodomain of MSX1. To determine whether the tooth agenesis phenotype may result from haploinsufficiency or a dominant-negative mechanism, we have performed biochemical and functional analyses of the mutant protein Msx1(R31P). We show that Msx1(R31P) has perturbed structure and reduced thermostability compared with wild-type Msx1. As a consequence, the biochemical activities of Msx1(R31P) are severely impaired, since it exhibits little or no ability to interact with DNA or other protein factors or to function in transcriptional repression. We also show that Msx1(R31P) is inactive in vivo, since it does not display the activities of wild-type Msx1 in assays of ectopic expression in the limb. Furthermore, Msx1(R31P) does not antagonize the activity of wild-type Msx1 in any of these assays. Because Msx1(R31P) appears to be inactive and does not affect the action of wild-type Msx1, we propose that the phenotype of affected individuals with selective tooth agenesis is due to haploinsufficiency.
authors.affiliation: Center for Advanced Biotechnology and Medicine, Piscataway, New Jersey 08854, USA.
authors.forename: G
authors.initials: G
authors.lastname: Hu
authors.forename: H
authors.initials: H
authors.lastname: Vastardis
authors.forename: A J
authors.initials: AJ
authors.lastname: Bendall
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Logan
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: C
authors.initials: C
authors.lastname: Nelson
authors.forename: S
authors.initials: S
authors.lastname: Stein
authors.forename: N
authors.initials: N
authors.lastname: Greenfield
authors.forename: C E
authors.initials: CE
authors.lastname: Seidman
authors.forename: J G
authors.initials: JG
authors.lastname: Seidman
authors.forename: C
authors.initials: C
authors.lastname: Abate-Shen
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001120:Arginine / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D001665:Binding Sites; D002645:Chickens; D004247:DNA / Q000378:metabolism; D005121:Extremities / Q000196:embryology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D051957:MSX1 Transcription Factor; D051379:Mice; D011392:Proline / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014071:Tooth Abnormalities / Q000235:genetics*; D014157:Transcription Factors
chemical_list: D018398:Homeodomain Proteins; D051957:MSX1 Transcription Factor; D014157:Transcription Factors; D004247:DNA; D001120:Arginine; D011392:Proline