This R308K point mutation in a highly conserved residue of the motor domain provides a model for studies into kinetochore-microtubule attachments, chromosome alignment, and the regulation of mitosis and meiosis.Read More +
KIF18A facilitates kinetochore-microtubule interactions and chromosome alignment. While KIF18A is very important in germ cell meiosis, it is not essential in somatic cell mitosis. This point mutation has incomplete penetrance and its impact differs with genetic background. In general, homozygotes are slightly smaller than normal and both males and females have germ cell depletion and diminished fertility. On average the ovaries have fewer oocytes and some homozygotes have tiny ovaries. The testes show spermatogenesis in some seminiferous tubules, but not others. This mutation shows variable penetrance and expressivity. On the C57BL/6J congenic background the penetrance of male sterility is only 37% while on the CAST/EiJ congenic background it increases to 90%. The number of primordial germ cells in the embryonic gonad is reduced by E11.5, post-migration, and is further reduced to scarcely a third the normal number by E15.5, after the proliferative phase. Heterozygous intercrosses yielded fewer than expected homozygotes, indicative of partial embryonic lethality. Homozygous mice on a segregating B6;CAST background were found to have reduced body weights as assessed between birth and 4 weeks of age and approximately 30% of homozygotes died by 4 weeks of age. (Reinholdt et al., 2006; Czechanski et al., 2015.)
Mouse embryonic fibroblasts (MEFs) from homozygotes grew slowly in culture and had reduced viability while MEFs from heterozygotes had an intermediate growth rate between that of homozygotes and controls. Homozygous MEFs progressed from nuclear envelope breakdown to anaphase with normal timing and did not show any increase in TUNEL staining or aneuploidy, but did have increased numbers of micronuclei most of which contained centromeres. Reticulocytes from homozygotes and heterozygotes were also shown to have an increased number of micronuclei with heterozygotes having a number of micronuclei intermediate between that of homozygotes and wildtype controls. (Fonesca et al., 2019.)
The germ cell depletion 2 mutation was induced in 129S1/Sv-Oca2+ Tyr+ Kitl+-derived CJ7 ES cells via a 16 hour exposure to ethylmethansulfonate. Treated ES cells were injected into C57BL/6J blastocysts and the chimeras were bred with C57BL/6J males. This strain had the mutation backcrossed to C57BL/6J, selecting for 129S1-derived flanking markers D2Mit58 and D2Mit274 at each generation. After reaching backcross generation N10 the maintenance breeding scheme became heterozygous intercrossing and in 2009 sperm was cryopreserved from heterozygous males at generation N10F4.
|Allele Name||germ cell depletion, John Schimenti|
|Allele Type||Chemically induced (other) (Null/Knockout)|
|Gene Symbol and Name||Kif18a, kinesin family member 18A|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|General Note||ES cells were mutagenized using ethyl methansulfonate (EMS). Generation 3 mice on a mixed 129S1/SvImJ and C57BL/6 background were identified by examining ductus deferens sperm for defects in morphology, motility, and quantity.|
|Molecular Note||The gcd2 mutation affects the highly conserved R308 residue within the KIF18A motor domain. The gcd2 mutation is a G-to-A transition in exon 7. This is a missense mutation that changes an AGA codon to an AAA, leading to the single amino acid change, R308K. Arginine 308 is a highly conserved amino acid in the motor domain of the protein.|
|Mutations Made By|| |
John Schimenti, Cornell University
While maintaining a live colony, these mice are bred by intercrossing heterozygotes. Mice homozygous for the mutation are have a high rate of sterility.
When using the B6.129S1-Kif18agcd2/JcsJ mouse strain in a publication, please cite the originating article(s) and include JAX stock #010508 in your Materials and Methods section.