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In Brief: Repro57 mice, bearing an Rnf212 gene mutation, exhibit infertility in both homozygous mutant males and females, revealing arrested spermatogenesis in males and investigating unclear mechanisms in females. The study highlights aneuploidy and altered kinetochore patterns in repro57 homozygous mutant oocytes, which impact later stages of embryo development., Abstract: Repro57 mice, induced with N-ethyl-N-nitrosourea and harboring a mutation in the Rnf212 gene, exhibit infertility in both homozygous mutant males and females. Rnf212 plays a crucial role in recombination and crossover designation. In male repro57 homozygous mutants, spermatocytes often degenerate during late prophase, and mature spermatozoa are absent in the seminiferous epithelium, indicating arrested spermatogenesis as the cause of infertility. Despite reports of infertility in Rnf212-knockout female mice, the specific mechanisms underlying infertility in female repro57 homozygous mutants remain elusive. This study investigates the chromosomal and kinetochore patterns of mature oocytes and their developmental potential following in vitro fertilization in female repro57 homozygous mutant mice. While all wild-type oocytes progress to metaphase II and exhibit euploidy, all repro57 homozygous mutant mouse oocytes display aneuploidy. Additionally, kinetochore distances in repro57 homozygous mutant oocytes exceed those observed in wild-type counterparts. Although no significant differences are noted in fertilization and early embryo development rates between wild-type and repro57 homozygous mutant mice, embryos derived from repro57 homozygous mutants exhibit significantly lower morula and blastocyst rates, accompanied by frequent cytokinesis failure and vacuole formation. These findings suggest that the premature segregation of sister chromatids in repro57 homozygous mutant mice adversely impacts the later stages of embryo development.

There are currently eight native horse populations in Japan, namely, Hokkaido, Kiso, Noma, Taishu, Misaki, Tokara, Miyako, and Yonaguni horses. Since locomotion traits, including gaitedness, are important for riding and packing horses, the genetic properties associated with these traits could be informative for understanding the characteristics and history of these horses. In this study, we investigated the distribution of the mutant allele of DMRT3 gene (DMRT3:p.Ser301Ter) associated with ambling gaits in the Japanese native horse. We also examined haplotypes of SNPs in the 83-kb region including DMRT3 gene by genotyping four SNPs in this region. The results revealed the presence of DMRT3:p.Ser301Ter in the Hokkaido and Yonaguni populations at allele frequencies of 0.18 and 0.02, respectively, and the observed haplotype associated with DMRT3:p.Ser301Ter was estimated as the most common haplotype in the horses in the world. Since DMRT3:p.Ser301Ter has been hypothesized to spread across Eurasian continent from Medieval England after 850 to 900 CE, our findings of the presence of DMRT3:p.Ser301Ter with the common haplotype in the Japanese native horses will provide a new insight into the history of the Japanese native horse, such as considerable level of gene flow from Eurasian continent after 850 to 900 CE., (© 2020 Japanese Society of Animal Science.)

The development of the axial skeleton is a complex process, consisting of segmentation and differentiation of somites and ossification of the vertebrae. The autosomal recessive skeletal fusion with sterility (sks) mutation of the mouse causes skeletal malformations due to fusion of the vertebrae and ribs, but the underlying defects of vertebral formation during embryonic development have not yet been elucidated. For the present study, we examined the skeletal phenotypes of sks/sks mice during embryonic development and the chromosomal localization of the sks locus. Multiple defects of the axial skeleton, including fusion of vertebrae and fusion and bifurcation of ribs, were observed in adult and neonatal sks/sks mice. In addition, we also found polydactyly and delayed skull ossification in the sks/sks mice. Morphological defects, including disorganized vertebral arches and fusions and bifurcations of the axial skeletal elements, were observed during embryonic development at embryonic day 12.5 (E12.5) and E14.5. However, no morphological abnormality was observed at E11.5, indicating that defects of the axial skeleton are caused by malformation of the cartilaginous vertebra and ribs at an early developmental stage after formation and segmentation of the somites. By linkage analysis, the sks locus was mapped to an 8-Mb region of chromosome 4 between D4Mit331 and D4Mit199. Since no gene has already been identified as a cause of malformation of the vertebra and ribs in this region, the gene responsible for sks is suggested to be a novel gene essential for the cartilaginous vertebra and ribs.

Natriuretic peptide receptor B (NPR-B), which has high affinity for C-type natriuretic peptide (CNP) and synthesizes intracellular cGMP, may be involved in gastrointestinal tract (GIT) regulation. A mutant allele of the NPR-B-encoding gene (Npr2) is responsible for the phenotype of the short-limb dwarfism (SLW) mouse. Homozygosity for this autosomal-recessive gene (slw/slw) leads to dwarfism and death before weaning because of milk retention in the stomach and intestinal distention. To elucidate the relationship between CNP/NPR-B signaling and GIT function, we investigated the association between Npr2 mutation and the GIT phenotype in slw/slw mice. The pylorus and large intestine of the mutants did not respond to CNP stimulation; further, they showed pyloric lumen narrowing with randomly aligned circular muscle cells. Comparison of the cGMP and neuronal marker distribution in GIT tissues confirmed cGMP expression in neuronal tissues. An Auerbach's plexus and submucosal tissues of the mutants didn't express cGMP and expressed Ca(2+). In contrast, those of normal mice (controls) expressed both cGMP and Ca(2+). Sequencing revealed that the causative Npr2 mutation was a 7-base deletion in exon 8, resulting in a frameshift and premature termination codon appearance. Therefore, the GIT phenotype of slw/slw mice is because of a CNP/NPR-B-signaling defect caused by an Npr2 mutation. These results facilitate better understanding of the role of CNP/NPR-B signaling in GIT motility.

A case of lysosomal storage disease has been reported in a calf of Japanese Black cattle. Lysosomal storage diseases are hereditary diseases caused by deficiency of lysosomal hydrolases. The clinical and pathological features and accumulated substrates of the affected animal indicated a possibility of sialidosis or galactosialidosis caused by deficiency of neuraminidase (NEU1) or protective protein for beta-galactosidase (PPGB). In the present study, we investigated nucleotide sequences of the genes encoding these two proteins to evaluate whether mutation of these genes is involved in this disease. We determined cattle genomic sequences of these two genes by using bovine EST sequences and the nucleotide sequences of all exons of these genes were compared between affected and normal animals. The results showed several nucleotide substitutions, but none of them was a functional mutation or specific to the affected animal. Furthermore, genotyping of the microsatellite markers in the vicinity of these two genes revealed no homozygosity of the chromosomal regions including these genes in the affected animal. These findings indicated that neither NEU1 nor PPGB gene is responsible for the lysosomal storage disease of Japanese Black cattle and therefore the disease is neither sialidosis nor galactosialidosis.

The hairy ears (Eh) mutation in the mouse originated from neutron irradiation experiments and is associated with chromosomal inversion on chromosome 15. Eh/+ mice have small pinna and extra hairs on the pinna but the phenotypic features of Eh/Eh mice are unclear. In this study we found that Eh/Eh mice died shortly after birth and had a cleft palate caused by impaired growth of palate shelves. Because genes located on the breakpoints of inversion are likely to be responsible for the defects associated with chromosomal inversions, we determined the breakpoints of the Eh inversion. We used a new genetic method that uses recombinant chromosomes resulting from crossing over between two overlapping inversions to determine the breakpoints. Koa is a mouse mutation associated with inversion of chromosome 15, which partially overlaps with the Eh inversion. We made Eh +/+ Koa double heterozygotes and obtained the recombinant chromosomes possessing deletion and duplication of the regions flanked by the breakpoints of both inversions, which were generated by crossing over within the overlapped region of these inversions. By defining the deleted regions we identified the breakpoints of the Eh inversion. We then examined the expression of genes in the vicinities of the breakpoints and found ectopic expression of the Hoxc5 gene and a transcript with unknown function in the developing palate of Eh/Eh mice, which is likely to be responsible for the cleft palate.

YPC is a mutant mouse strain with defective hair growth characterized by thin, short hairs and poorly developed hair bulbs and dermal papillae. To identify the gene associated with the phenotype, we performed genome-wide linkage analysis using 1010 backcross progeny and 123 microsatellite markers covering all chromosomes. The mutant locus (ypc) was mapped to a 0.2-cM region in the proximal part of mouse chromosome 1. This 0.2-cM region corresponds to a 450-kb region of genome sequence that contains two genes with known functions and five ESTs or predicted genes with unknown functions. Sequence analysis revealed a single C-to-A nucleotide substitution at nucleotide 1382 in the Sgkl gene, causing a nonsense mutation at codon 461. Sgkl encodes serum and glucocorticoid-inducible kinase-like kinase (SGKL), which belongs to a subfamily of serine/threonine protein kinases and has been suggested to have a role downstream of lipid signals produced by activation of phosphoinositide 3-kinase (PI3K). In the mutant SGKL, a serine residue in the C-terminal end of the protein (Ser486), which is indispensable for activation of SGKL upon phosphorylation, is abolished by premature termination. Specific expression of the Sgkl gene in the inner root sheath of growing hair follicles was also identified by in situ hybridization. Therefore, we concluded that the nucleotide substitution in the Sgkl gene is the causative mutation for defective hair growth in the ypc mutant mouse and that the signaling pathway involving SGKL plays an essential role in mammalian hair development.

In the breeding of domestic animals, selection of economically desired traits has been the most important consideration for the improvement of animals, but excluding negative factors in animal production, such as causative genes for hereditary diseases, is also required for the genetic improvement of domestic animals. The incidence of various hereditary diseases has been reported in Japanese beef cattle and these diseases have caused serious problems in the breeding and raising of healthy beef cattle. This article reviews the identification of causative genes for the following three hereditary diseases in Japanese beef cattle: (i) Chediak–Higashi syndrome; (ii) renal tubular dysplasia; and (iii) bovine chondrodysplastic dwarfism. Chediak–Higashi syndrome is a hereditary bleeding disorder reported in Japanese black cattle. To identify the cause of this disease, we cloned and sequenced the bovine LYST gene, which has been found to be involved in Chediak–Higashi syndrome in humans, and found that an amino acid substitution of histidine to arginine at amino acid residue 2015 is the causative mutation in the cattle disease. Renal tubular dysplasia is a hereditary disease of Japanese black cattle showing renal failure and growth retardation. We mapped the locus for this disease to the 4 cM region of bovine chromosome 1 by linkage analysis and found a large deletion in this region. The deleted region contained the PCLN1 gene encoding a tight-junction protein of renal epithelial cells, and we concluded that deletion of the PCLN1 gene is responsible for the disease. Bovine chondrodysplastic dwarfism is a hereditary disease of Japanese brown cattle, displayed by short limbs and joint abnormalities. We mapped the locus for the disease to a region of bovine chromosome 6 by linkage analysis. By constructing YAC and BAC contigs covering this region and sequence analysis, we identified a novel gene ( LIMBIN), which plays an essential role in bone formation in this region, and found two mutations responsible for the disease. The identification of these mutations provided the basis for DNA-based diagnostic systems for these three diseases, and after development of the diagnosis systems, the incidences of these hereditary diseases have dramatically decreased. [ABSTRACT FROM AUTHOR]

Abstract: Multiple ocular defects (MOD) in cattle is an autosomal recessive hereditary disorder characterized by dysplasia of the lens, retinal detachment, persistence of the hyaloid artery, and microphthalmia. The locus responsible for MOD has been mapped to the proximal region of bovine chromosome 18. In the present study, we refined the localization of the MOD locus to a 1.0-Mb interval by haplotype analysis using a pedigree of affected animals. Comparison of nucleotide sequence of genes in this region revealed a one-nucleotide insertion in the WFDC1 gene, which resulted in a frame shift mutation and premature termination codon at the middle of the protein. WFDC1 is a small secretory protein containing a WAP-type four disulfide core domain. Specific expression of Wfdc1 was observed in the lens, retina, and optic nerves of embryonic and adult mouse eyes by immunohistochemical staining and in situ hybridization. The present finding demonstrated the essential role of WFDC1 in mammalian eye development. [Copyright &y& Elsevier]