A Novel Homozygous Nonsense Variant in BICD2 Underlies Hereditary Spastic Paraplegia Complex Type

Hereditary spastic paraplegia (HSP) are a group of genetically and clinically diverse neurodegenerative ailments with distinguishing feature of lower limbs spasticity and upper motor neuron degeneration. BICD2 is an adaptor protein which regulates the cellular trafficking of cargo molecules crucial for motor neuron growth and maturation. In present study, a Pakistani family of HSP penetrating in autosomal recessive pattern was ascertained. Patients presented spasticity and stiffness of upper and lower limbs, severe microcephaly, dysphagia, no speech, hearing loss and seizures. Genome wide linkage analysis and whole exome sequencing revealed a novel homozygous nonsense mutation (c.204T>G) in BICD2 gene which was predicted to yield a truncated protein product (p. Glu68*). This is first nonsense mutation being reported causing HSP with complex clinical features and early onset. Further, functional exploration will be required for genotype phenotype correlation.