The spdh/spdh mutants have a normal body size but exhibit shortened, fused, and duplicated digits in both front and rear feet. Ossification is severely delayed and ossification centers are mis-patterned in developing metacarpal, metatarsal and phalangeal bones. Joint formation is severely disrupted in the phalanges, with forelimbs more affected compared to the hindlimbs. Reduced rates of proliferation and differentiation of mutant chondrocytes contribute to altered cartiledge/bone morphology. Although expression patterns of Hoxd13/11/12 and Hoxa13 do not seem to be disrupted, their function does seem to be disrupted, indicating HOX protein interactions are altered as a result of the spdh mutation. Additionally, the spdh mutant phenotype is much more severe than mutants carrying a targeted disruption of the spdh gene, supporting a dominant-negative effect. The preputial glands of the genital tract are absent in both male and female spdhmutants (Albrecht et al., 2002; Johnson et al., 1998; Dolle et al., 1993).
The Hoxd13spdhmice were discovered in the B6C3Fe-a/a-Csflop colony at the Mouse Mutant Resource of The Jackson Laboratory in 1994. Malformations of the foot were initially noted with an inheritance pattern consistent with an autosomal recessive mutation. Through linkage and PCR typing analyses it was determined that the mutation lies on chromosome 2 and originated within a chromosomal region from C3FeLe.B6-a. Hoxd13spdhmice are maintained on the B6C3Fe-a/a background by outcrossing a homozygous female to B6C3FeF1 a/a (stock # 001022) each generation, then intercrossing the obligate heterozygous offspring. Csflop has been bred out of the strain. The Hoxd13spdh/Hoxd13spdh males are infertile. (Johnson et al., 1998; Albrecht et al., 2002). Embryos for this strain were frozen as a product of breeding B6C3FeF1-a/a females with heterozygous males at N44F1.
|Allele Name||synpolydactyly homolog|
|Gene Symbol and Name||Hoxd13, homeobox D13|
|Strain of Origin||B6C3Fe a/a-Csf1op/J|
|Molecular Note||21 bp in-frame duplication within a polyalanine-encoding region at the 5'-end of the Hoxd13 coding sequence. This duplication expands the stretch of alanines from 15 to 22, the same type of expansion that occurs in human synpolydactyly mutations.|
When using the synpolydactyly homolog mouse strain in a publication, please cite the originating article(s) and include JAX stock #002875 in your Materials and Methods section.