Mice homozygous for this ENU-induced mutation contain a loss-of-function mutation in exon 3 of the Sema3a gene and may be useful in studying proper patterning connectivity and guidance of neurons of the peripheral nervous system.
David D. Ginty, Harvard Medical School
Mice homozygous for this ENU-induced mutation (Sema3am808Ddg), are viable and fertile. These mice contain a loss-of-function mutation in exon 3 of the Sema3a (sema domain, immunoglobulin domain (Ig), short basic domain, secreted, (semaphorin) 3A) gene. Sema3a encodes a secreted protein that interacts with neuropilin-2 and plays a critical role in normal neuronal pattern development of the peripheral nervous system. These Sema3aK108N homozygotes exhibit defasciculation and overgrowth of peripheral axonal projections of the spinal nerves and of axons within the ophthalmic branch of the trigeminal ganglia. Sensory and motor projections comprising the ulnar and radial nerves also extend beyond their targets and travel in bundles that are disorganized and defasciculated. These mutant mice may be useful in studying proper patterning connectivity and guidance of neurons of the peripheral nervous system.
Male C57BL/6 mice were treated with multidose N-ethyl-N-nitrosourea (ENU) and then bred to C3H/He females. The resulting male pups were then bred to C3H/He females to obtain second generation mice. The resulting female offspring were subsequently bred back to their parental line to obtain third generation mice. A mutagenesis screen was then performed to select mice with mutations effecting peripheral nervous system patterning. A forward-genetic screen approach found a mutation in the sema domain, immunoglobulin domain (Ig), short basic domain, secreted, (semaphorin) 3A (Sema3a) gene. Sequencing of this gene identified founder line 808 with an A to T transversion in exon 3 resulting in a lysine to asparagine loss-of-function mutation (K108N). The donating investigator reported that these mice were backcrossed to C3H/He mice for at least eight generations (see SNP note below). Upon arrival at The Jackson Laboratory, mice were bred to C3H/HeJ (Stock No. 000659) for at least one generation to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. 13 of the 27 markers throughout the genome were segregating between C3H/HeJ and B6J, suggesting an incomplete backcross.
|Allele Name||mutation 808, David D Ginty|
|Allele Type||Chemically induced (ENU)|
|Gene Symbol and Name||Sema3a, sema domain, immunoglobulin domain (Ig), short basic domain, secreted, (semaphorin) 3A|
|Strain of Origin||C57BL/6|
|Molecular Note||ENU mutagenesis induced an A to T transversion at position that results in the amino acid substitution of asparagine for lysine at position 108 (K108N). The protein product is predicted to poorly interact with the Npn-1/PlexA holoreceptor.|
|Mutations Made By|| |
David Ginty, Harvard Medical School
When maintaining a live colony, homozygous mice may be bred together.
When using the Sema3a