Genetic Predictors of Synbrachydactyly and Complex Skeletal Syndromes in Miniature Pinschers: Rationale for Implementing Whole Genome Sequencing and Multi-Locus DNA Screening

Abstract Background. Hereditary anomalies of limb skeletal development in dogs present a significant challenge for modern purebred breeding programs. In the Miniature Pinscher population, cases of digital phalanx shortening and deformity (brachydactyly) are routinely documented. Recent phenotypic monitoring within the breed has revealed that this defect often co-segregates with incomplete cutaneous syndactyly (soft-tissue webbing), central paw clefting (ectrodactyly), and marked fusion or vertical transposition of the digital and metacarpal/metatarsal pads (conjoined/cloven paw phenotype). In veterinary practice, this complex phenotype is frequently misclassified as an isolated cosmetic flaw or a consequence of early trauma, leading to systematic neglect of the issue and uncontrolled dissemination of a potentially lethal, systemic skeletal disorder within the breed. Objectives. To establish a scientific rationale for the polyetiological genetic and syndromic nature of synbrachydactyly in Miniature Pinschers, and to demonstrate the necessity of implementing advanced Whole Genome Sequencing (WGS) and multi-locus DNA screening protocols. Hypothesis. This paper presents an expanded rationale linking distal limb deformities and soft-tissue digital pad fusion in Miniature Pinschers to a singular syndromic continuum driven by pleiotropic effects or variable expressivity within master regulatory pathways of embryogenesis. The author shifts the phenotypic focus from isolated phalanx shortening to upstream disruptions of interdigital apoptosis and cellular polarity, linking these peripheral signs to the cryptic carriage of mutations within seven key loci: ROR2, BMPR1B, DVL2, KRT5, TP63, BMP4, and LRP4. These cascades can induce severe, life-threatening axial skeletal anomalies (IVDD, cervical/thoracic hemivertebrae, lumbosacral transitional vertebrae - LTV) and congenital heart defects. Practical Significance. Documented population data reveals juvenile mortality at approximately 10 months of age across two distinct, genetically isolated breeding lines due to compressive cervical myelopathy secondary to cervical hemivertebrae. This severe outcome co-segregates with lines carrying or producing the brachydactyly phenotype, validating the use of digital anomalies and conjoined paw pads as an explicit proxy for lethal spinal defects. A revised step-by-step diagnostic interpretation algorithm for DNA test results and a specialized selective mating matrix for breeders are proposed, integrating the newly introduced epithelial and joint-segmentation profiles. Implementing the suggested testing panel will enable the timely elimination of deleterious alleles from the core breeding population while preserving the broader genetic diversity of the Miniature Pinscher breed. Keywords: Miniature Pinscher, brachydactyly, synbrachydactyly, cloven paw phenotype, conjoined paw pads, cervical hemivertebrae, lumbosacral transitional vertebra, LTV, ROR2, BMPR1B, DVL2, KRT5, TP63, LRP4, Robinow-like syndrome, DNA screening, veterinary genetics.