New variants and genotype–phenotype correlation in KIF5A mutation: the contribution of a large Italian cohort

Background: Variants in the Kinesin-family member 5A (KIF5A) gene are associated with a range of motor diseases, and a strong correlation between the protein domains (motor, stalk and tail) and the clinical phenotype has been proposed. However, several studies have reported exceptions contributing to a complex genotype-phenotype correlation in recent years. Further studies are needed to improve our knowledge about the prevalence of KIF5A variants and their genotype-phenotype correlation. Methods: 390 patients (220 hereditary spastic paraplegia, 80 Charcot-Marie-Tooth disease type 2 and 90 amyotrophic lateral sclerosis) have been selected for next-generation sequencing Clinical Exome. Results: Five patients have been found to carry causative variants in the KIF5A gene. Of these, three are familiar cases, and two are sporadic. Segregation analysis was performed on the familiar probands. The five patients with pathogenic variants represent 4% of the studied population, and the clinical and genetic analysis of these five families allowed us to examine different scenarios.Some of these data support the hypothesis of a complex correlation between domains and disease. Conclusion: These data confirm the complex genotype-phenotype correlation, both in terms of clinical heterogeneity associated with a specific domain and variability within the members of the same family, but also suggest a strong genotype-phenotype correlation, both intrafamiliar and interfamiliar, produced by a few variants.