From the 2,053 samples analyzed, three were found to have apparent chromosome aneuploidies (Figure 1 and Figure 2). Specifically, one dog was found with monosomy X (Fig. 1C), one dog with trisomy X (Fig. 1D) and one dog with probable mosaic, trisomy CFA38 (Canis Familiaris chromosome 38) (Fig. 2B). Four puppies from the mosaic, trisomy 38 dog were tested on the SNP array and all had normal diploid results for CFA38 (data not shown).
Monosomy X (77,X)
The puppy was one of five pups born to a miniature poodle mother and a goldendoodle (golden retriever poodle mix) father. The pup was visibly smaller than littermates, weighing 9.5 ounces at 1 week and 16 ounces at 2 weeks of age (Table 1). The puppy was able to nurse, but required supplemental bottle or tube feeding for the first week of life. None of the other pups in the litter required supplemental feeding. Physical exam at 2 months, 23 days showed persistent, bilateral, pupillary membranes, but otherwise healthy. The puppy was spayed at this time prior to the first estrous. Breeder reported that the pup, now one year of age at the time of this report, has caught up with her siblings for both height and weight. Examination of photographs provided by the breeder, in comparison to siblings, showed no obvious dysmorphic features (data not shown). Figure 1C shows the plots for the SNP array data. As in human microarray data, monosomy X shows complete homozygosity for the A or B allele, including probes in the PAR.
Trisomy X (79,XXX)
The puppy is a Papillon born in a litter of three pups. She is currently an intact female, 18 months old and has not entered into a first estrous, which normally occurs around 9 – 11 months of age. As compared to her brother and sister, she is of appropriate size and has no known health problems. The breeder reports that the pup is nondysmorphic and meets the breed standard for conformation with the exception of a low-set tail, which is considered a fault in the breed. Developmentally, the pup seems lagging as compared to her sibs and other Papillons in the household, according to the breeder who is also a human developmental specialist. Behaviorally, the pup is sweet, docile and not as quick to learn or train in the breeder’s experience. Figure 1D shows the plot for the trisomy X dog. As with human microarray data, the entire X chromosome, including the PAR, shows B allele frequencies (BAF) as either AAA, AAB, BBA or BBB.
Mosaic Trisomy 38 (78,XY/mos 79,XY,+38)
The intact, adult male dog is of mixed breed origin. The dog has proven fertility in that he has sired two litters. He is reportedly in good health. Examination of photographs did not show any obvious dysmorphic features (data not shown). Figure 2B shows the plots for chromosomes 36, 37 and 38. The BAF for CFA38 are intermediate to those expected for a full (nonmosaic) trisomy (refer to Fig. 1D for comparison with the trisomy X case), indicating likely mosaicism. Cytogenetic or FISH analysis was not possible, so the mosaicism could not be confirmed and an unbalanced Robertsonian translocation or isochromosome could not be excluded.