Stunted; A Short Face Mutation on Chromosome 19 in the Mouse
Michelle Curtain, Julie Hurd, Leah Rae Donahue
Source of support: National Institutes of Health, EYO15073
Mutation Symbol: stn
Mutation Name: stunted
Strain of Origin: C57BL/6J
Current Strain Name: C57BL/6-stn/J
Stock #: 004507 (view JAX® Mice Data Sheet for additional information including Price and Supply Information) Note: As of Sept 8, 2008 Cryo only.
Phenotype Category: craniofacial, coat color
Origin and Description
The stunted mutation was discovered in a production colony of C57BL/6J mice at The Jackson Laboratory. Mutants have short faces. (see photo) Also, 95 % of mutants have a white belly spot; screening 40 mice, 38 had this coat color defect. About 14% of the colony developed hydrocephaly (24 out of 164 mice screened). Mice with hydrocephalus are not used for colony maintenance.
Stunted mutants are viable and fertile. The colony is maintained by homozygote crossed to homozygote matings. There are no longer controls in the colony.
Genetic Analysis
stn is inherited as an autosomal recessive mutation proven by mating mutants together and having all offspring affected.
For linkage analysis, a backcross was used with a DBA/2J inbred mated to a C57BL/6-stn/J mutant. F1 hybrids were backcrossed to an stn/stn. The N2 progeny were visually phenotyped and spleens and tail tips were collected from both mutants and heterozygotes. Following our standard mapping protocol, the mutation maps to Chromosome 19 between markers D19Mit13 and D19Mit91. This spans 33 cM to 47 cM or, more precisely, 31.9 Mb to 47.9Mb. An allele test was done with Papss2, which maps in this same region of Chromosome 19. Papss2 is not allelic with stn. Allele tests were also done with diminutive (dm) and stubby (stb) and were not allelic.
Pathology
Routine Pathological Screening was done on a 7-week-old male stn/stn and a 5 ½ -week-old male stn/stn. No lesions were found. Another male at 5 ½ weeks had severe hydrocephalus and rosettes in the retina.
An ophthalmoscope was used to view the eyes of three 3-month-old stn/stn male and female mutants. (Eye Mutant Resource) One male and one female had retinal spots on the left eye. The other male had normal eyes. Six 5-week-old males and females were examined. Three females and one male were normal and two females had half rings around the optic nerve in the right eye.
Hearing was assessed by auditory brainstem response (ABR) threshold analysis. The ABR results showed that two 3-month-old stn/stn males had normal hearing but two other 3-month-old stn/stn males had moderate or greater hearing loss. An ear cross section was also done on an stn/stn. The inner ear was okay but it did have otitis media.
Discussion
Stunted mice have a shortened face and the high incidence white belly spots in mutants appear to be a part of the stunted phenotype. Also, if hydrocephaly is a part of the stunted mutation or if it is segregating as a different mutation, past attempts to breed hydrocephaly out of the colony resulted in the striking short face phenotype to diminish concluding that hydrocephaly may be a part of the stunted phenotype.
Acknowledgements
For their expertise and assistance, we wish to thank:
Eva Eicher's lab: Mapping the mutation
Coleen Marden: Pathology
Rod Bronson, PhD: Pathology Evaluation
Norm Hawes: Evaluation of Eyes
Heping Yu: Hearing Assessment
Qing Yin Zheng, PhD: Otiis Media Screen
