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Description and genetic mapping of Polypodia: an X-linked dominant mouse mutant with ectopic caudal limbs and other
Jessica A Lehoczky1, Wei-Wen Cai, Julie A Douglas
1Department of Human Genetics, University of Michigan, Ann Arbor, Michigan 48109-0618, USA.
Abstract:
In this report we present a spontaneous mouse mutant, named Polypodia (Ppd), that primarily exhibits ectopic, ventral/caudal limbs and associated pelvic girdle malformation or duplication. Less penetrant features include diphallia, microphthalmia, small kidney, curled or kinked tail, forelimb anomaly, and skin papillae. Ppd mice have a normal karyotype and no large-scale genomic deletions or insertions by BAC-based array comparative genomic hybridization (CGH). Ppd is X-linked dominant with approximately 20% penetrance on the C3H background and maps to X:61.6 Mb-X:71.24 Mb. The limb and a subset of the nonlimb anomalies are similar to those in offspring from retinoic acid-treated dams at E4.5-5.5 and feature overlap with the Disorganization mouse mutant and human patients with ectopic legs. We hypothesize that Ppd affects very early steps in the formation of caudal structures including limb and appendage number. The existence of noncaudal anomalies implies the involvement of Ppd in a broad array of cell fate decisions.
Insights
A new mouse mutant, Polypodia (Ppd), displays extra limbs and pelvic malformations. This X-linked dominant mutation impacts early development of caudal structures and cell fate.
Area of Science:
- Developmental biology
- Genetics
- Teratology
Background:
- Spontaneous mutations provide valuable insights into gene function during development.
- Understanding the genetic basis of limb development is crucial for diagnosing and treating congenital abnormalities.
Purpose of the Study:
- To characterize a novel spontaneous mouse mutant, Polypodia (Ppd), with ectopic limb development.
- To determine the genetic basis and inheritance pattern of the Ppd mutation.
- To investigate the developmental mechanisms underlying the observed anomalies.
Main Methods:
- Phenotypic analysis of the Ppd mouse mutant.
- Karyotyping and BAC-based array comparative genomic hybridization (CGH) to assess genomic integrity.
- Genetic mapping of the mutation to a specific chromosomal region.
- Comparison with known developmental mutants and human conditions.
Main Results:
- The Ppd mutant exhibits primary features of ectopic ventral/caudal limbs and pelvic girdle malformation/duplication.
- Less penetrant phenotypes include diphallia, microphthalmia, kidney anomalies, tail defects, and skin papillae.
- Ppd is an X-linked dominant mutation with incomplete penetrance, mapping to mouse chromosome X.
- Genomic analysis revealed no large-scale deletions or insertions.
Conclusions:
- The Ppd mutation likely affects early developmental processes in caudal structure formation, including limb and appendage patterning.
- The presence of non-caudal anomalies suggests the gene's involvement in broader cell fate determination pathways.
- Ppd serves as a model for studying ectopic limb development and associated congenital anomalies.
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