Hair length in mammals is generally regulated by the hair cycle, and its disruption leads to abnormal hair morphogenesis in several species. FGF5, one of the hair cycle regulators, has a role in inducing catagen, and that mutation causes abnormal hair length in both sexes in humans, mice, dogs, and cats. Male-dominant long-haired coat (MALC) is an inbred strain of Syrian hamster exhibiting spontaneous long hair in males. After castration, MALC exhibited significantly shorter hair than the control individuals, but testosterone administration to castrated MALC showed reversion to the original phenotype. Moreover, flutamide administration led to MALC phenotype repression. Histological analysis revealed that hair follicle regression was shown in the wild-type 4 weeks after depilation, but that of MALC remained in the anagen phase. We detected a c.546delG of Fgf5 in MALC (Fgf5malc) that might lead to truncation resulting from a frame shift in FGF5 (p.Arg184GlyfsX6). Additionally, homozygous Fgf5malc was only detected in long-haired (Slc:Syrian×MALC)F2 and (J-2-Nn×MALC)F2 progenies, and all homozygous wild and heterozygous Fgf5malc individuals showed normal hair length. Thus, Fgf5malc leads to male-dominant long hair via a prolonged anagen phase which is affected by testosterone in hamsters. To our knowledge, this report is the first to present the sexual dimorphism of hair length caused by the Fgf5 mutation.

We discovered a new cataract mutation, kfrs4, in the Kyoto Fancy Rat Stock (KFRS) background. Within 1 month of birth, all kfrs4/kfrs4 homozygotes developed cataracts, with severe opacity in the nuclei of the lens. In contrast, no opacity was observed in the kfrs4/+ heterozygotes. We continued to observe these rats until they reached 1 year of age and found that cataractogenesis did not occur in kfrs4/+ rats. To define the histological defects in the lenses of kfrs4 rats, sections of the eyes of these rats were prepared. Although the lenses of kfrs4/kfrs4 homozygotes showed severely disorganised fibres and vacuolation, the lenses of kfrs4/+ heterozygotes appeared normal and similar to those of wild-type rats. We used positional cloning to identify the kfrs4 mutation. The mutation was mapped to an approximately 9.7-Mb region on chromosome 7, which contains the Mip gene. This gene is responsible for a dominant form of cataract in humans and mice. Sequence analysis of the mutant-derived Mip gene identified a 5-bp insertion. This insertion is predicted to inactivate the MIP protein, as it produces a frameshift that results in the synthesis of 6 novel amino acid residues and a truncated protein that lacks 136 amino acids in the C-terminal region, and no MIP immunoreactivity was observed in the lens fibre cells of kfrs4/kfrs4 homozygous rats using an antibody that recognises the C- and N-terminus of MIP. In addition, the kfrs4/+ heterozygotes showed reduced expression of Mip mRNA and MIP protein and the kfrs4/kfrs4 homozygotes showed no expression in the lens. These results indicate that the kfrs4 mutation conveys a loss-of-function, which leads to functional inactivation though the degradation of Mip mRNA by an mRNA decay mechanism. Therefore, the kfrs4 rat represents the first characterised rat model with a recessive mutation in the Mip gene.

Summary:Purpose: We characterized and evaluated as an animal model of epilepsy NER, a new epileptic rat strain, which was developed by inbreeding rats with spontaneous tonic-clonic seizures in a stock of Crj:Wistar.Methods: Animals were monitored through the inbreeding course, and video-EEGs were recorded selectively. External seizure-provoking stimuli were applied to NER and to a control parental strain. FI, F2, and backcross progenies were produced between NER and a nonepileptic unrelated strain. Pathologic study included hematoxylin-and-eosin (HE), Kliiver-Barrera's, modified Bodian silver, and neo-Timm's staining.Results: After the F9 generation, 94%-98% of NER exhibited spontaneous tonic-clonic convulsions, beginning with neck and forelimb clonus, wild jumpinghnning, opisthotonic posturing, and evolving to tonic, then clonic convulsion, followed by postictal flaccidity. Most seizure onsets occurred between 2 4 months of age, and the incidence was 0.45 k 0.21 seizures in 12 h. Ictal cortical and hippocampal EEGs were characterized by high-voltage spikes followed by diffuse spike-andwave or polyspike-and-wave complexes. NER revealed seizure susceptibility to pentylenetetrazol, tossing, and transcorneal electroshock, but not to tactile, photic, or acoustic stimuli, or to transauricular electroshock. Mating experiments revealed that 0% (0146) of the animals in F1,25.5% (1315 1) in F2, and 63.6%(56/88) in backcross progenies exhibited spontaneous tonicclonic convulsions without sex difference. For all these epileptic traits, no pathologic changes were demonstrated in the CNS.Conclusions: NER frequently exhibited spontaneous convulsions, controlled by a major autosomal recessive gene for epilepsy, that are comparable to generalized tonic-clonic seizures in humans. This can serve as a new genetic model in epilepsy research.

A recent report showed higher oxygen consumption, adenosine triphosphate (ATP) production and mitochondrial localisation in trophectoderm cells than in the inner cell mass of mouse blastocysts. We hypothesised that this phenomenon was due to the asymmetrical distribution of mitochondria in the blastomeres during the earlier stages. Oocytes, 2-cell embryos and 4-cell embryos were analysed to determine the volume, ATP content and mitochondrial DNA (mtDNA) copy number in the whole egg and individual blastomeres. Significant differences were detected in the volumes of cytoplasm and ATP contents between blastomeres from the 2-cell and 4-cell embryos. Moreover, whilst remaining stable in whole embryos, mtDNA copy number differed between blastomeres, indicating that mitochondria in oocytes are unevenly delivered into the daughter blastomeres during the first two cleavages. Although their volume and ATP content were not correlated, there was a significant correlation between volume and mtDNA copy number in 2- and 4-cell blastomeres. These results indicate that the number of mitochondria delivered to blastomeres during early cleavage is not precisely equal, suggesting that the allocation of mitochondria into daughter blastomeres is affected by uneven cytoplasmic distribution during cytokinesis in the oocyte and mother blastomeres.

An investigation was performed on a method for detecting abnormalities in central nervous system, viscera and skeletons in chicken embryos. The examination of the nervous system and viscera was performed on embryos that had been fixed with BOUIN's solution for more than a week, basically accoding to the methods of WILSON (1965) or BARROW & TAYLOR (1969) designed for mammalian fetuses, but with occasional modifications when required. As a result, the present procedure proved to be an excellent method. When 6-aminonicotinamide was injected into yolk sac, hypoplasia of the heart in one case, hypoplasia of the left hepatic lobe in another case were found, indicating the effectiveness of this method as a teratological test. To examine the skeleton, embryos fixed with ethanol were skinned, defatted in acetone, cleared with 1% aqueous KOH containing 0.1% H2O2, and stained with alizarin red S. As a result, good stained specimens were obtained. Skeletal specimens were also prepared from 6-aminonicotinamide-treated embryos. These specimens revealed fused cervical vertebrae, fused lumbosacral vertebrae, delayed ossification of the caudal vertebrae, uncinate process, sternebrae, and digitus manus bones. These findings indicate that this method can serve as a useful teratological test.