B6C3Fe a/a-Lmx1a^dr-J/J

Stock number: 000636
Product name: dreher Jackson
Research areas: Developmental Biology Research, Neurobiology Research, Sensorineural Research

Description

These mice carry a spontaneous mutation at the Lmx1a locus characterized by the appearance of a tiny filament at the tip of the tail which disappears by 2 days after birth leaving either a short tail or distinctly blunted tail. Mutyants also display reduced size of the cerebellum with unusual patterns of folliation, and a delayed development of the righting reflex and hyperactivity.

Detailed description

Lmx1a encodes a LIM homeodomain (LIM-hd) protein that is expressed in the roof plate along the neuraxis during CNS development. The Lmx1a^dr-J mutation replaces a conserved cysteine in the LIM1 domain of the protein with a tyrosine (Millonig et al. 2000).

Mice homozygous for Lmx1a^dr-Jare identifiable at birth by a thin filament extending from the end of the tail, which drops off within a few days, and a short or blunt tail. They may also have a head bleb. When fur develops, there may be a white belly spot. Lmx1a^dr-J/Lmx1a^dr-J mice are ataxic and hyperactive and have difficulty righting themselves, and they do not reproduce (Sweet and Wahlsten 1983). They also exhibit circling behavior, are deaf, and have inner ear and vertebral malformations (Manzanares et al. 2000).

Lmx1a^dr-J homozygotes exhibit defects of three classes of anatomic structures: the hindbrain roof plate, neural crest derived tissues, and the axial skeleton. Failure of roofplate development results in absence of dorsal interneurons of the spinal cord and of granule neurons of the cerebellar cortex and failure of the dorsal vertebral neural arches to form (Millonig et al. 2000). The cerebellum is smaller than normal, in some cases virtually absent, and exhibits disrupted foliation (Sweet and Wahlsten 1983; Sekiguchi et al. 1992). The cytoarchitectural organization of the neocortex, the hippocampus and the dentate gyrus is disrupted (Sekiguchi et al. 1992, 1993, 1994, 1996). Skeletal anomalies include abnormal neural crest derived cranial bones and improper fusion of cervical and thoracic vertebrae at the dorsal midline (Mananares et al. 2000). Deafness may be the consequence of "serious morphogenetic defects of the otic vesicle due to the dorsal neural tube abnormalities," perhaps augmented by "abnormal sensory and motor projections" in the region of rhombomeres 4-6 (Manzanares et al. 2000). Although they have no external or behavioral phenotype, 50% of heterozygotes exhibit histological pathology of the hippocampus qualitatively similar, but less extensive, than that of homozygotes (Patrylo et al. 1990).

Development

The Lmx1a^dr-J mutation, originally called sst^J and later known as dr^sst-J and as dr^J, arose in the C3FeB6-A/A^w-J-ank colony in the Mouse Mutant Stocks Center at The Jackson Laboratory (Sweet and Wahlsten 1983). Since its discovery, it has been maintained by crossing ovary transplant recipients to B6C3Fe-a/a males; the black coat color of the present background makes it easy to distinguish pups derived from the transplanted ovary from any that might result from residual host ovarian tissue. Identification of the alleles for markers flanking Lmx1a in Lmx1a^dr-J/Lmx1a^dr-J progeny of B6C3Fe a/a-Lmx1a^dr-J/J pairs demonstrated that the mutation occurred on the C3H chromosome (Millonig et al. 2000).

Allele

Symbol: a
Name: nonagouti
MGI accession ID: MGI:1855937
Generation method: Spontaneous
Marker symbol: a
Marker name: nonagouti
Chromosome: 2
Strain of origin: old mutant of the mouse fancy
Molecular note: Characterization of this allele shows an insertion of DNA comprised of a 5.5kb virus-like element, VL30, into the first intron of the agouti gene. The VL30 element itself contains an additional 5.5 kb sequence, flanked by 526 bp of direct repeats (beta4 retroviral sequence). The host integration site is the same as for a^t-2Gso and A^w-38J and includes a duplication of four nucleotides of host DNA and a deletion of 2 bp from the end of each repeat. Northern analysis of mRNA from skin of homozygotes shows a smaller agouti message and levels 8 fold lower than found in wild-type.
General note: Insertion of the LV30 retrotransposon without the beta4 retrovirus sequence does not cause the nonagouti phenotype. J:278039

Allele

Symbol: Lmx1a^dr-J
Name: dreher Jackson
MGI accession ID: MGI:1888413
Generation method: Spontaneous
Marker symbol: Lmx1a
Marker name: LIM homeobox transcription factor 1 alpha
Chromosome: 1
Strain of origin: C3FeB6 A/A^w-J-Ank^ank/J
Molecular note: A G-to-A transition mutation results in a conserved cysteine to a tyrosine amino acid change at position 82 (p.C82Y) in the LIM1 domain of the encoded protein. The conserved cysteine is thought to be required for coordination of zinc that is essential for the function of the LIM domain, and thus the transcriptional activity of the protein.