Hereditary hydrocephalus internus in a laboratory strain of golden hamsters (Mesocricetus auratus)

Golden hamsters of one common laboratory strain had a high incidence of hydrocephalus internus. When a severity score of hydrocephalus was used, a major autosomal recessive locus could be identified. However, when a binary score (hydrocephalus, no hydrocephalus) was used, no such major locus could be detected and results of test matings were not consistent with Mendelian inheritance. Golden hamsters with severe forms of hydrocephalus had a dorsally compressed and ventrally intact hippocampus. Implications for the behavior and well-being of affected hamsters are unknown but researchers using this strain should be aware of the likely presence of hydrocephalu

Frameshift Variant in MFSD12 Explains the Mushroom Coat Color Dilution in Shetland Ponies

Mushroom is a unique coat color phenotype in Shetland Ponies characterized by the dilution of the chestnut coat color to a sepia tone and is hypothesized to be a recessive trait. A genome wide association study (GWAS), utilizing the Affymetrix 670K array (MNEc670k) and a single locus mixed linear model analysis (EMMAX), identified a locus on ECA7 for further investigation (Pcorrected = 2.08 × 10−10). This locus contained a 3 Mb run of homozygosity in the 12 mushroom ponies tested. Analysis of high throughput Illumina sequencing data from one mushroom Shetland pony compared to 87 genomes from horses of various breeds, uncovered a frameshift variant, p.Asp201fs, in the MFSD12 gene encoding the major facilitator superfamily domain containing 12 protein. This variant was perfectly concordant with phenotype in 96 Shetland Ponies (P = 1.15 × 10−22), was identified in the closely related Miniature Horse for which the mushroom phenotype is suspected to occur (fmu = 0.02), and was absent in 252 individuals from seven additional breeds not reported to have the mushroom phenotype. MFSD12 is highly expressed in melanocytes and variants in this gene in humans, mice, and dogs impact pigmentation. Given the role of MFSD12 in melanogenesis, we propose that p.Asp201fs is causal for the dilution observed in mushroom ponies

Congenital Sensorineural Deafness in Australian Stumpy-Tail Cattle Dogs Is an Autosomal Recessive Trait That Maps to CFA10

Congenital sensorineural deafness is an inherited condition found in many dog breeds, including Australian Stumpy-tail Cattle Dogs (ASCD). This deafness is evident in young pups and may affect one ear (unilateral) or both ears (bilateral). The genetic locus/loci involved is unknown for all dog breeds. The aims of this study were to determine incidence, inheritance mechanism, and possible association of congenital sensorineural deafness with coat colour in ASCD and to identify the genetic locus underpinning this disease.A total of 315 ASCD were tested for sensorineural deafness using the brain stem auditory evoked response (BAER) test. Disease penetrance was estimated directly, using the ratio of unilaterally to bilaterally deaf dogs, and segregation analysis was performed using Mendel. A complete genome screen was undertaken using 325 microsatellites spread throughout the genome, on a pedigree of 50 BAER tested ASCD in which deafness was segregating. Fifty-six dogs (17.8%) were deaf, with 17 bilaterally and 39 unilaterally deaf. Unilaterally deaf dogs showed no significant left/right bias (p = 0.19) and no significant difference was observed in frequencies between the sexes (p = 0.18). Penetrance of deafness was estimated as 0.72. Testing the association of red/blue coat colour and deafness without accounting for pedigree structure showed that red dogs were 1.8 times more likely to be deaf (p = 0.045). The within family association between red/blue coat colour and deafness was strongly significant (p = 0.00036), with red coat colour segregating more frequently with deafness (COR = 0.48). The relationship between deafness and coat speckling approached significance (p = 0.07), with the lack of statistical significance possibly due to only four families co-segregating for both deafness and speckling. The deafness phenotype was mapped to CFA10 (maximum linkage peak on CFA10 -log10 p-value = 3.64), as was both coat colour and speckling. Fine mapping was then performed on 45 of these 50 dogs and a further 48 dogs (n = 93). Sequencing candidate gene Sox10 in 6 hearing ASCD, 2 unilaterally deaf ASCD and 2 bilaterally deaf ASCD did not reveal any disease-associated mutations.Deafness in ASCD is an incompletely penetrant autosomal recessive inherited disease that maps to CFA10

Sire Evaluation by Only Extended Partial Milk and Fat Records

The standard of comparison for dairy production records is the 305-day lactation, and much research has been directed to estimating 305-day milk and fat records from incomplete or in-progress records. This study was to determine the effect of several methods of extending incomplete records on sire evaluation. Complete 305-day milk and fat records of first lactations of 73,724 daughters of 1,362 artificial insemination Holstein sires processed at the New York Dairy Records Processing Laboratory were used to compute sire proofs for yield of milk and fat. Partial records of two lengths (60 to 80 days and 130 to 160 days) on the same daughters were extended by three methods, and sire proofs were computed from these six sets of extended records. Correlations between sire proofs with complete records only and sire proofs with only extended incomplete records were .93 or .94 (for milk proofs) when the length of the part record was between 130 and 160 days, regardless of the method of extension. Correlations were less (.66 to .81 for milk proofs), as expected, when the length of the part record was between 60 and 80 days

Monte Carlo Study of Genetic Groups in Sire Evaluation

Fixed genetic groups have been defined arbitrarily in linear models for sire evaluation. This simulation examined genetic groups under several selection strategies. Sires with highest estimated transmitting abilities were selected to have sons and additional female progeny. The process of evaluation and selection of sires and dams was continued for four generations. Final estimates of transmitting ability were compared to actual transmitting ability for several sire evaluation models on 300 simulated data sets. Genetic groups defined by generation increased the accuracy of estimating sire transmitting abilities over ignoring genetic groups when selected dams and sires of young bulls were mated. A joint selection model was presented which assists in interpreting results of simulation

Genetic Groups in Dairy Sire Evaluation Under a Selection Model

The frequently arbitrary application and definition of genetic groups makes sire grouping the “weak link” of the sire evaluation process. A selection model for records not in the model for observations is similar in form to the genetic groups model. Implications of this correspondence are discussed and illustrated through a small example. Guidelines for possible grouping strategies also are discussed