Genetic mapping of the polled/intersex locus (PIS) in goats

Polled Intersex Syndrome with urethral atresia in a goat

A 5-day-old hornless goat was referred with dysuria since birth. The scrotum was absent, and a small penis-like structure was seen below the perineal raphe. On the laparotomy, the testicles were found near the inguinal ring- and attached to a uterus-like structure. On histological analysis, the uterus-like structure was blind-end. Germ cells were absent in the testis. The karyotype of this goat was 60, XX and the SRY gene was absent. The goat was homozygous for a DNA deletion responsible for the Polled Intersex Syndrome (PIS). To the authors' knowledge, this is the first report as the clinical case of the PIS-/- goat with urethral atresia.

Bilateral Leydig Cell Tumor in a Six-Year-Old Intersex Goat Affected by Polled Intersex Syndrome

A 6-year-old, sterile, Blanca Celtibérica breed adult doe was referred to our faculty. The doe had external female genitalia, a short anogenital distance, and normally shaped udders. Masculinization signs in the head shape and male behavior were also noted at the time of referral. Genetic analysis demonstrated normal 2n = 60 XX karyotype and an absence of the sex-determining region Y (SRY). The animal was homozygous for a DNA deletion responsible for the Polled Intersex Syndrome (PIS). A uterus and 2 uterine horns were present at the postmortem examination. Gartner's ducts and degenerated Wolffian derivatives persisted. There were 2 intra-abdominal testicle-like structures, one of which consisted of epididymal and deferent ducts. An advanced Leydig cell tumor, resulting in almost total destruction of the intratesticular structures, was also observed. Leydig cell tumors usually produce testosterone. Thus, these histologic findings are compatible with the evident virilization.

Characterization of Pisrt1/Foxl2 in Ellobius lutescens and exclusion as sex-determining genes

The rodent Ellobius lutescens is an exceptional mammal which determines male sex constitutively without the SRY gene and, therefore, may serve as an animal model for human 46,XX female-to-male sex reversal. It was suggested that other factors of the network of sex-determining genes determine maleness in these animals. However, some sex-determining genes like SOX9 and SF1 have already been excluded by segregation analysis as primary sex-determining factors in E. lutescens. In this work, we have cloned and characterized two genes of the PIS (polled intersex syndrome) gene interval, which were reported as candidates in female-to-male sex reversal in hornless goats recently. The genes Foxl2 and Pisrt1 from that interval were identified in E. lutescens DNA and mapped to Chromosome 8. We have excluded linkage of Foxl2 and Pisrt1 loci with the sex of the animals. Hence, the involvement of this gene region in sex determination may be specific for goats and is not a general mechanism of XX sex reversal or XX male sex determination.

SRY-negative XX sex reversal in a pony: a case report

A three year old pony with sexually ambiguous external genitalia was found to have a normal female karyotype (64, XX) and bilateral inguinal testes. The PCR analysis of blood samples revealed the absence of the Y chromosome sequences SRY, eTSPY and ZFY. No Y chromosome sequences were identified in DNA extracted from the gonads. The mechanism whereby XX sex reversal occurs in the absence of SRY is unknown.

Sry-negative XX sex reversal in purebred dogs

The gene responsible for testis induction in normal male mammals is the Y-linked Sry. However, there is increasing evidence that other genes may have testis-determining properties. In XX sex reversal (XXSR), testis tissue develops in the absence of the Y chromosome. Previous polymerase chain reaction (PCR) assays indicated that autosomal recessive XXSR in the American cocker spaniel is Sry-negative. In this study, genomic DNA from the breeding colony of American cocker spaniels and from privately owned purebred dogs were tested by PCR using canine primers for the Sry HMG box and by Southern blots probed with the complete canine Sry coding sequence. Sry was not detected by either method in genomic DNA of affected American cocker spaniels or in the majority (20/21) of affected privately owned purebred dogs. These results confirm that the autosomal recessive form of XXSR in the American cocker spaniel is Sry-negative. In combination with previous studies, this indicates that Sry-negative XXSR occurs in at least 15 dog breeds. The canine disorder may be genetically heterogeneous, potentially with a different mutation in each breed, and may provide several models for human Sry-negative XXSR. A comparative approach to sex determination should be informative in defining the genetic and cellular mechanisms that are common to all mammals.

Sry-negative XX true hermaphrodite in a Basset hound

A true hermaphrodite was diagnosed in a 7-mo.-old Basset hound. The diagnosis was based on the clinical signs, the histology of the gonads and the karyogram. Additionally, the dog was tested for the Y-linked gene Sry, which was negative. The Basset hound presented here is compared to other XX sex reversed animals described in the literature. In man, XX sex reversal is a heterogenous condition. The pathogenesis in Sry-negative individuals is not understood. Thus Sry-negative animals could serve as an animal model of the human disease.

High-resolution human/goat comparative map of the goat polled/intersex syndrome (PIS): the human homologue is contained in a human YAC from HSA3q23

The genetic and cytogenetic map around the chromosome 1 region shown to be linked with polledness and intersexuality (PIS) in the domestic goat (Capra hircus) was refined. For this purpose, a goat BAC library was systematically screened with primers from human coding sequences, scraped chromosome 1 DNA, bovine microsatellites from the region, and BAC ends. All the BACs (n = 30) were mapped by fluorescence in situ hybridization (FISH) on goat chromosome 1q41-q45. The genetic mapping of 30 new goat polymorphic markers, isolated from these BACs, made it possible to reduce the PIS interval to a region of less than 1 cM on goat chromosome 1q43. The PIS locus is now located between the two genes ATP1B and COP, which both map to 3q23 in humans. Genetic, cytogenetic, and comparative data suggest that the PIS region is now probably circumscribed to an approximately 1-Mb DNA segment for which construction of a BAC contig is in progress. In addition, a human YAC contig encompassing the blepharophimosis-ptosis-epicanthus-inversus region was mapped by FISH to goat chromosome 1q43. This human disease, mapped to HSA 3q23 and affecting the development and maintenance of ovarian function, could be a potential candidate for goat PIS.

Comparative gene mapping: a fine-scale survey of chromosome rearrangements between ruminants and humans

A total of 202 genes were cytogenetically mapped to goat chromosomes, multiplying by five the total number of regional gene localizations in domestic ruminants (255). This map encompasses 249 and 173 common anchor loci regularly spaced along human and murine chromosomes, respectively, which makes it possible to perform a genome-wide comparison between three mammalian orders. Twice as many rearrangements as revealed by ZOO-FISH were observed. The average size of conserved fragments could be estimated at 27 and 8 cM with humans and mice, respectively. The position of evolutionary breakpoints often correspond with human chromosome sites known to be vulnerable to rearrangement in neoplasia. Furthermore, 75 microsatellite markers, 30 of which were isolated from gene-containing bacterial artificial chromosomes (BACs), were added to the previous goat genetic map, achieving 88% genome coverage. Finally, 124 microsatellites were cytogenetically mapped, which made it possible to physically anchor and orient all the linkage groups. We believe that this comprehensive map will speed up positional cloning projects in domestic ruminants and clarify some aspects of mammalian chromosomal evolution.

Construction and extensive characterization of a goat bacterial artificial chromosome library with threefold genome coverage

A goat Bacterial Artificial Chromosome (BAC) library of 61,440 independent clones was constructed and characterized. The average size of the inserts was estimated at 153 kilobases by analyzing almost 500 clones using Not1 digestion followed by FIGE (Field Inverted Gel Electrophoresis) analysis. The library represents about three genome equivalents, which yields a theoretical probability of 0.95 of isolating a particular DNA sequence. After individual growth, the clones were arrayed in 40 superpools, which were organized in three dimension pools. A rapid technique for pool DNA preparation by microwave treatment was set up. This technique was compatible with PCR analysis. Primer pairs from 166 sequences (microsatellites, coding sequences from goat, and conserved Expressed Sequence Tags (ESTs) from humans) enabled the library to be successfully searched in 165 cases, with an average of 3.52 positive superpools. Only one sequence could not be found. The degree of chimerism was evaluated by FISH analysis with DNA from over 110 clones and was estimated at 4%. This BAC library will constitute an invaluable tool for positional cloning in ruminants, as well as for more general comparative mapping studies in mammals.