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Several hundred disease-causing mutations are currently known in domestic dogs. Breeding management is therefore required to minimize their spread. Recently, genetic methods such as direct-to-consumer testing have gained popularity; however, their effects on dog populations are unclear. Here, we aimed to evaluate the influence of genetic testing on the frequency of mutations responsible for canine degenerative myelopathy and assess the changes in the genetic structure of a Pembroke Welsh corgi population from Japan. Genetic testing of 5,512 dogs for the causative mutation in superoxide dismutase 1 (SOD1) (c.118G>A (p.E40K)) uncovered a recent decrease in frequency, plummeting from 14.5% (95/657) in 2019 to 2.9% (24/820) in 2022. Weir and Cockerham population differentiation (F ST) based on genome-wide single-nucleotide polymorphism (SNP) of 117 selected dogs detected the SNP with the highest F ST located in the intron of SOD1 adjacent to the c.118G>A mutation, supporting a selection signature on SOD1. Further genome-wide SNP analyses revealed no obvious changes in inbreeding levels and genetic diversity between the 2019 and 2022 populations. Our study highlights that genetic testing can help inform improved mating choices in breeding programs to reduce the frequency of risk variants and avoid inbreeding. This combined strategy could decrease the genetic risk of canine degenerative myelopathy, a fatal disease, within only a few years. [ABSTRACT FROM AUTHOR]

It is known that in the silkworm (Bombyx mori), males have two Z sex chromosomes whereas females have Z and W and the W chromosome has a dominant role in female determination; here a single female-specific W-chromosome-derived PIWI-interacting RNA is shown to be the feminizing factor in B. mori. The silkworm feminizing factor Susumu Katsuma and colleagues have answered a question that has perplexed insect geneticists for more than eight decades -- how does the W chromosome determine femaleness in the silkworm Bombyx mori and many other Lepidoptera? In this system, males have two Z sex chromosomes and females have one Z and one W. The authors show that the feminizing factor is a single W chromosome-derived PIWI-interacting RNA (piRNA). The piRNA silences the product of a gene located on the Z chromosome (named Masc) that encodes a CCCH-type zinc finger protein. This silencing is in turn important for the production of female-specific isoforms of the doublesex gene that acts at the downstream end of the sex differentiation cascade in the embryo. In male embryos Masc protein controls both dosage compensation and masculinization. The silkworm Bombyx mori uses a WZ sex determination system that is analogous to the one found in birds and some reptiles. In this system, males have two Z sex chromosomes, whereas females have Z and W sex chromosomes. The silkworm W chromosome has a dominant role in female determination.sup.1,2, suggesting the existence of a dominant feminizing gene in this chromosome. However, the W chromosome is almost fully occupied by transposable element sequences.sup.3,4,5, and no functional protein-coding gene has been identified so far. Female-enriched PIWI-interacting RNAs (piRNAs) are the only known transcripts that are produced from the sex-determining region of the W chromosome.sup.6, but the function(s) of these piRNAs are unknown. Here we show that a W-chromosome-derived, female-specific piRNA is the feminizing factor of B. mori. This piRNA is produced from a piRNA precursor which we named Fem. Fem sequences were arranged in tandem in the sex-determining region of the W chromosome. Inhibition of Fem-derived piRNA-mediated signalling in female embryos led to the production of the male-specific splice variants of B. mori doublesex (Bmdsx), a gene which acts at the downstream end of the sex differentiation cascade.sup.7,8. A target gene of Fem-derived piRNA was identified on the Z chromosome of B. mori. This gene, which we named Masc, encoded a CCCH-type zinc finger protein. We show that the silencing of Masc messenger RNA by Fem piRNA is required for the production of female-specific isoforms of Bmdsx in female embryos, and that Masc protein controls both dosage compensation and masculinization in male embryos. Our study characterizes a single small RNA that is responsible for primary sex determination in the WZ sex determination system., Author(s): Takashi Kiuchi [sup.1] , Hikaru Koga [sup.1] , Munetaka Kawamoto [sup.1] , Keisuke Shoji [sup.1] , Hiroki Sakai [sup.2] , Yuji Arai [sup.1] , Genki Ishihara [sup.1] , Shinpei [...]