Kaczmarska Adriana, Christen Matthias, Del Caño-Ochoa Francisco, Ramon-Maiques Santiago, Miro Ana Cloquell, Rupp Angie, Jagannathan Vidhya, Leeb Tosso, Gutierrez-Quintana Rodrigo
School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, Glasgow, G61 1QH, UK.
Vetsuisse Faculty, Institute of Genetics, University of Bern, Bremgartenstrasse 109a, 3001, Bern, Switzerland.
Sci Rep. 2025 Apr 18;15(1):13506. doi: 10.1038/s41598-025-98414-0.
Developmental and epileptic encephalopathy type 50 (DEE50) in humans is a severe early-onset neurometabolic disorder caused by biallelic loss-of-function variants in the CAD gene encoding a key multi-enzymatic protein for de novo pyrimidine nucleotide synthesis. Untreated, the condition is often fatal, but patients respond to uridine supplementation, which fuels nucleotide synthesis through CAD-independent salvage pathways. Here, we report a novel variant in the feline CAD gene in a 4-month-old Bengal kitten with intractable seizures and abnormal behavior. The variant, XP_011279586.1:p.(Ser2015Asn), was predicted to affect the oligomerization of the C-terminal aspartate transcarbamylase (ATCase) domain of CAD. Genotyping of 110 unaffected Bengal cats revealed four additional carriers of the mutant allele, confirming its presence in the breed. In a CAD-knockout human cell line dependent on uridine, the recombinant expression of human wildtype CAD, but not of the Asn2015 mutant, restored cell growth without uridine, demonstrating that the p.Ser2015Asn variant disrupts CAD function and is pathogenic. This study facilitates genetic testing of carriers and affected cats and suggests that uridine supplementation could be a potential treatment. Furthermore, CAD-deficient Bengal cats might serve as a valuable spontaneous large animal model to further investigate the pathogenic mechanisms of this rare epileptic encephalopathy in humans.
人类50型发育性和癫痫性脑病(DEE50)是一种严重的早发性神经代谢紊乱疾病,由CAD基因的双等位基因功能丧失变异引起,该基因编码一种用于从头嘧啶核苷酸合成的关键多酶蛋白。未经治疗,这种疾病通常是致命的,但患者对尿苷补充有反应,尿苷通过不依赖CAD的补救途径为核苷酸合成提供原料。在这里,我们报告了一只4个月大的孟加拉小猫的猫CAD基因中的一个新变异,该小猫患有顽固性癫痫和异常行为。该变异体XP_011\279586.1:p.(Ser2015Asn)预计会影响CAD C末端天冬氨酸转氨甲酰酶(ATCase)结构域的寡聚化。对110只未受影响的孟加拉猫进行基因分型,发现另外有4只携带突变等位基因的猫,证实了该突变在该品种中的存在。在依赖尿苷的CAD基因敲除人类细胞系中,人类野生型CAD的重组表达(而非Asn2015突变体的重组表达)恢复了无尿苷情况下的细胞生长,表明p.Ser2015Asn变异破坏了CAD功能且具有致病性。这项研究有助于对携带突变的猫和患病猫进行基因检测,并表明尿苷补充可能是一种潜在的治疗方法。此外,CAD缺陷的孟加拉猫可能成为一种有价值的自发大型动物模型,以进一步研究这种人类罕见癫痫性脑病的致病机制。