RESUMEN
Inherited disorders of sexual development (DSD) cause sterility and infertility in horses. Mutations causing such disorders have been identified in other mammals, but there is little information on the molecular causes in horses. While the equine genome sequence has made it possible to identify candidate genes, additional tools are needed to routinely screen them for causative mutations. In this study, we designed a screening panel of polymerase chain reaction primer pairs for 15 equine genes. These are the candidate genes for testicular or ovotesticular XX DSD and XY DSD, the latter of which includes gonadal dysgenesis, androgen insensitivity syndrome (AIS), persistent Mullerian duct syndrome and isolated cryptorchidism. Six horses with testicular or ovotesticular XX DSD and controls were screened. In addition, candidate genes for androgen insensitivity syndrome, persistent Mullerian duct syndrome and isolated cryptorchidism were screened in normal horses. While no sequence variants were uniquely associated with XX DSD, the 38 sequence variants identified can serve as intragenic markers in genome-wide association studies or linkage studies to hasten mutation identification in equine XX DSD and XY DSD.
Asunto(s)
Trastornos del Desarrollo Sexual/veterinaria , Variación Genética/genética , Enfermedades de los Caballos/genética , Mutación , Cromosoma X/genética , Cromosoma Y/genética , Síndrome de Resistencia Androgénica/genética , Síndrome de Resistencia Androgénica/veterinaria , Animales , Secuencia de Bases , Criptorquidismo/genética , Criptorquidismo/veterinaria , Trastorno del Desarrollo Sexual 46,XY/genética , Trastorno del Desarrollo Sexual 46,XY/veterinaria , Trastornos del Desarrollo Sexual/genética , Femenino , Disgenesia Gonadal/genética , Disgenesia Gonadal/veterinaria , Caballos , Masculino , Reacción en Cadena de la Polimerasa/veterinariaRESUMEN
In persistent Müllerian duct syndrome (PMDS), Müllerian ducts fail to regress in males during sexual differentiation. In the canine miniature schnauzer model, PMDS is caused by a C to T transition in exon 3 of the Müllerian inhibiting substance type II receptor (MISRII), which introduces a DdeI restriction site. Here we report a molecular diagnostic test for PMDS in the miniature schnauzer to identify affected dogs and carriers. As our test results suggest that the mutation is identical by descent in affected dogs of this breed, the test could be used to eliminate this mutation from the miniature schnauzer breed worldwide.
Asunto(s)
Trastornos del Desarrollo Sexual/veterinaria , Enfermedades de los Perros/diagnóstico , Técnicas de Diagnóstico Molecular/métodos , Conductos Paramesonéfricos/patología , Animales , Secuencia de Bases , Enzimas de Restricción del ADN/metabolismo , Trastornos del Desarrollo Sexual/diagnóstico , Perros , Exones/genética , Datos de Secuencia MolecularRESUMEN
This report details a case of SRY-negative XX sex reversal in a mixed breed dog and surveys affected dogs of several breeds for mutations in RSPO1 coding regions. Genomic DNA from the mixed breed case was evaluated for mutations in candidate genes. Sequencing identified a homozygous G to A transition in RSPO1 exon 4 that changes a highly conserved amino acid codon in the thrombospondin domain. The possibility that this was a single nucleotide polymorphism (SNP) could not be excluded by genotyping family members. Therefore, the coding region of RSPO1 was sequenced in a survey of affected dogs, which identified a T to C transition (exon 3) in some, the above G to A transition (exon 4) in others, and no change in the remaining affected dogs. Genotypes at these base pair positions were not uniquely associated with the affected phenotype in any breed, indicating the identified transitions are most likely SNPs, not causative mutations for this canine disorder. However, the possibility that polymorphisms play a modifier role, such as changing threshold or severity of phenotypic expression in a mixed breed dog, cannot be excluded. This study emphasizes the importance of canine pedigree, breed, and population studies in evaluating candidate mutations.
Asunto(s)
Cruzamiento , Trastornos del Desarrollo Sexual , Perros/genética , Mutación/genética , Sistemas de Lectura Abierta/genética , Proteína de la Región Y Determinante del Sexo/genética , Trombospondinas/genética , Secuencia de Aminoácidos , Animales , Emparejamiento Base , Secuencia de Bases , Análisis Citogenético , Perros/clasificación , Exones/genética , Femenino , Inmunohistoquímica , Masculino , Datos de Secuencia Molecular , Estructura Terciaria de Proteína , Testículo/citología , Trombospondinas/químicaRESUMEN
Canine Sry-negative XX sex reversal is a disorder of gonadal development wherein individuals having a female karyotype develop testes or ovotestes. In this study, linkage mapping was undertaken in a pedigree derived from one proven carrier American cocker spaniel founder male and beagle females. All affected dogs in the analysis were XX true hermaphrodites and confirmed to be Sry negative by polymerase chain reaction. A genome-wide linkage screen conducted using 245 microsatellite markers revealed highest LOD score of 3.4 (marker CPH9) on CFA29. Fine mapping with additional microsatellites in the region containing CPH9 localized the Sry-negative XX sex reversal locus to a 5.4-Mb candidate region between markers CPH9 and FH3003 (LOD score 3.15). Insignificant LOD scores were found at genome-wide screen or fine mapping markers that were within 10 Mb of 45 potential candidate genes reported to have a role in mammalian sex determination or differentiation. Together, these results suggest that a novel locus on CFA29 may be responsible for sex reversal in this pedigree.
Asunto(s)
Mapeo Cromosómico , Trastornos del Desarrollo Sexual , Perros/genética , Genoma , Cromosoma X , Animales , Femenino , Marcadores Genéticos , Genotipo , Masculino , LinajeRESUMEN
In mammals, the Y-linked SRY gene is normally responsible for testis induction, yet testis development can occur in the absence of Y-linked genes, including SRY. The canine model of SRY-negative XX sex reversal could lead to the discovery of novel genes in the mammalian sex determination pathway. The autosomal genes causing testis induction in this disorder in dogs, humans, pigs, and horses are presently unknown. In goats, a large deletion is responsible for sex reversal linked to the polled (hornless) phenotype. However, this region has been excluded as being causative of the canine disorder, as have WT1 and DMRT1 in more recent studies. The purpose of this study was to determine whether microsatellite marker alleles near or within five candidate genes (GATA4, FOG2, LHX1, SF1, SOX9) are associated with the affected phenotype in a pedigree of canine SRY-negative XX sex reversal. Primer sequences flanking nucleotide repeats were designed within genomic sequences of canine candidate gene homologues. Fluorescence-labeled polymorphic markers were used to screen a subset of the multigenerational pedigree, and marker alleles were determined by software. Our results indicate that the mutation causing canine SRY-negative XX sex reversal in this pedigree is unlikely to be located in regions containing these candidates.
Asunto(s)
Trastornos del Desarrollo Sexual , Repeticiones de Microsatélite/genética , Cromosoma X/genética , Animales , Perros , Factor de Transcripción GATA4/genética , Genes sry/genética , Proteínas del Grupo de Alta Movilidad/genética , Proteínas de Homeodominio/genética , Linaje , Reacción en Cadena de la Polimerasa , Receptores Citoplasmáticos y Nucleares/genética , Factor de Transcripción SOX9 , Factor Esteroidogénico 1 , Factores de Transcripción/genéticaRESUMEN
XX sex reversal is known in 17 breeds of dogs. In the American cocker spaniel, it segregates as an autosomal recessive trait, and the affected animals lack the testis determining Sry gene. In the search for an autosomal gene that causes this trait, we considered the possibility of Lhx9, a gene encoding LIM homeobox containing transcription factor 9, as a candidate gene. An American cocker spaniel pedigree showing Sry-negative XX sex reversal phenotype was genotyped with an intronic Lhx9 microsatellite marker. Segregation of the Lhx9 marker in the pedigree indicated that a mutation in canine Lhx9 is not likely to be the cause of Sry-negative XX sex reversal. In addition, using the recently available 7.6X canine genomic sequence, we report the location and genomic organization of canine Lhx9.
