Primers and probes used in the analysis.

Skeletal dysplasias encompass a diverse group of genetic disorders characterized by short stature and dwarfism. In humans, 771 types of skeletal dysplasia have been documented. Similar forms of these disorders have also been observed in dogs. The first cases of documented skeletal dysplasia in Dalmatian dogs were reported in the early 1980s, with additional affected dogs observed in subsequent years. Careful radiological and histopathological examinations at the time revealed severe limb deformities, including shortened radii and ulnae, irregular growth plates and disrupted endochondral ossification. In this study, we applied whole-genome sequencing on samples collected in 1992 and identified a genetic variant in the PRKG2 gene, introducing a premature stop codon (XM_038582312: c.1601T > G, p.L534X). Genetic variants in PRKG2 have previously been implicated in human acromesomelic dysplasia, a disorder affecting limb growth in young children. The PRKG2-encoded protein plays a crucial role in endochondral ossification, and if translated, the identified nonsense variant would result in a truncated protein lacking most of the catalytic domain. Extended screening of the genetic variant revealed its continued segregation in the current Dalmatian population. Furthermore, three recent cases of dwarfism in Dalmatians were found to be homozygous for the identified PRKG2 nonsense variant. These findings provide compelling evidence for the role of PRKG2 in Dalmatian dwarfism, resolving a decades-old genetic mystery in the breed.

骨骼发育异常（skeletal dysplasias）是一类以身材矮小与侏儒症为核心表型的多样化遗传性疾病集合。目前人类中已记录的骨骼发育异常类型共计771种，在犬类中也发现了与之表型相似的同类疾病。大麦町犬（Dalmatian）骨骼发育异常的首例临床记录于20世纪80年代初被报道，后续数年又陆续发现了更多患病个体。彼时通过细致的放射影像学与组织病理学检查，确认患病犬存在严重肢体畸形，具体表现为桡骨与尺骨缩短、生长板不规则以及软骨内骨化（endochondral ossification）过程紊乱。
本研究对1992年采集的样本开展全基因组测序（whole-genome sequencing），在PRKG2基因中鉴定出一处可引入提前终止密码子的遗传变异：XM_038582312: c.1601T>G，p.L534X。此前已有研究证实，PRKG2基因的遗传变异与人类肢中型肢体发育不良（acromesomelic dysplasia）相关，该疾病会影响幼儿的肢体生长发育。PRKG2编码的蛋白在软骨内骨化过程中发挥关键作用；若该变异对应的转录本完成翻译，所产生的截短蛋白将丢失大部分催化结构域。
对该遗传变异的扩大筛查显示，其在当前大麦町犬种群中仍处于孟德尔分离遗传状态。此外，近期确诊的3例大麦町犬侏儒症病例，均为该PRKG2无义变异（nonsense variant）的纯合子。本研究结果为PRKG2基因在大麦町犬侏儒症的发病机制中发挥关键作用提供了确凿证据，解开了该犬种数十年来悬而未决的遗传谜题。