A Common Missense Variant Causing Factor XI Deficiency and Increased Bleeding Tendency in Maine Coon Cats

Development and validation of animal variant classification guidelines to objectively evaluate genetic variant pathogenicity in domestic animals

Assessing the pathogenicity of a disease-associated genetic variant in animals accurately is vital, both on a population and individual scale. At the population level, breeding decisions based on invalid DNA tests can lead to the incorrect inclusion or exclusion of animals and compromise the long-term health of a population, and at the level of the individual animal, lead to incorrect treatment and even life-ending decisions. Criteria to determine pathogenicity are not standardized, i.e., no guidelines for animal variants are available. Here, we aimed to develop and validate guidelines to be used by the community for Mendelian disorders in domestic animals to classify variants in categories based on standardized criteria. These so-called animal variant classification guidelines (AVCG) were based on those developed for humans by The American College of Medical Genetics and Genomics (ACMG). In a direct comparison, 83% of the pathogenic variants were correctly classified with ACMG, while this increased to 92% with AVCG. We described methods to develop datasets for benchmarking the criteria and identified the most optimal in silico variant effect predictor tools. As the reproducibility was high, we classified 72 known disease-associated variants in cats and 40 other disease-associated variants in eight additional species.

The spectrum of factor XI deficiency in Southeast China: four recurrent variants can explain most of the deficiencies

BACKGROUND

Factor XI (FXI) deficiency is an autosomal hemorrhagic disorder characterized by reduced plasma FXI levels. Multiple ancestral variants in the F11 gene have been identified in Ashkenazi Jews and other selected European populations. However, there are few reports of predominant variants in Chinese and/or East Asian populations. The aim of this study is to characterize the genotypes and phenotypes of FXI deficiency and identify the predominant variants.

RESULTS

Of the 41 FXI-deficient patients, 39 exhibited severe FXI defects, considerably more than those with partial defects. The APTT levels showed a negative correlation with FXI activity levels (coefficient=-0.584, P < .001). Only nine patients experienced mild bleeding, including one partially defective patient and eight severely defective patients. The majority of patients were referred for preoperative screenings (n = 22) and checkups (n = 14). Genetic analysis revealed that 90% of the patients had genetic defects, with 2, 16, and 19 cases of heterozygous, homozygous, and compound heterozygous patients, respectively. Seventeen variants were detected in the F11 gene (6 novel), including eleven missense variants, four nonsense variants, and two small deletions scattered throughout the F11. Of the 11 missense variants, six have not yet been studied for in vitro expression. Protein modeling analyses indicated that all of these variants disrupted local structural stability by altering side-chain orientation and hydrogen bonds. Nine variants, consisting of three missense and six null variants, were detected with a frequency of two or more. The highest allele frequency was observed in p.Q281* (21.25%), p.W246* (17.50%), p.Y369* (12.50%), and p.L442Cfs*8 (12.50%). The former two were variants specific to East Asia, while the remaining two were southeast China-specific variants.

CONCLUSION

Our population-based cohort demonstrated that no correlation between the level of FXI activity and the bleeding severity in FXI deficiency. Additionally, the prevalence of FXI deficiency may have been underestimated. The nonsense p.Q281* was the most common variant in southeast China, suggesting a possible founder effect.

[Unilateral othematoma as the only symptom in a dog with multiple myeloma]

An acute, unilateral othematoma was diagnosed in a 9-year-old mixed-breed dog. There was no clinical or anamnestic evidence for the cause of the othematoma. During diagnostic work-up, marked hyperglobulinemia and marked thrombocytopenia were detected. This was a consequence of a multiple myeloma. This is the first case report of a dog with othematoma secondary to coagulopathy associated with multiple myeloma.