Gain-of-Function KIDINS220 Variants Disrupt Neuronal Development and Cause Cerebral Palsy

BACKGROUND

Kinase D-interacting substrate of 220 kDa (KIDINS220) is a multifunctional scaffolding protein essential for neuronal development. It has been implicated in neurological diseases with either autosomal dominant (AD) or autosomal recessive (AR) inheritance patterns. The molecular mechanisms underlying the AR/AD dual nature of KIDINS220 remain elusive, posing challenges to genetic interpretation and clinical interventions. Moreover, increased KIDINS220 exhibited neurotoxicity, but its role in neurodevelopment remains unclear.

OBJECTIVE

The aim was to investigate the genotype-phenotype correlations of KIDINS220 and elucidate its pathophysiological role in neuronal development.

METHODS

Whole-exome sequencing was performed in a four-generation family with cerebral palsy. CRISPR/Cas9 was used to generate KIDINS220 mutant cell lines. In utero electroporation was employed to investigate the effect of KIDINS220 variants on neurogenesis in vivo.

RESULTS

We identified in KIDINS220 a pathogenic nonsense variant (c.4177C > T, p.Q1393*) that associated with AD cerebral palsy. We demonstrated that the nonsense variants located in the terminal exon of KIDINS220 are gain-of-function (GoF) variants, which enable the mRNA to escape nonsense-mediated decay and produce a truncated yet functional KIDINS220 protein. The truncated protein exhibited significant resistance to calpain and consequently accumulated within cells, resulting in the hyperactivation of Rac1 and defects in neuronal development.

CONCLUSIONS

Our findings demonstrate that the location of variants within KIDINS220 plays a crucial role in determining inheritance patterns and corresponding clinical outcomes. The proposed interaction between Rac1 and KIDINS220 provides new insights into the pathogenesis of cerebral palsy, implying potential therapeutic perspectives. © 2023 International Parkinson and Movement Disorder Society.

Pre- and Postnatal Characterization of Autosomal Recessive KIDINS220-Associated Ventriculomegaly

Introduction

Heterozygous loss-of-function variants in the last 2 exons of KIDINS220 have been associated with spastic paraplegia, intellectual disability, nystagmus, and obesity (SINO). Syndromic features of this condition include macrocephaly and dilatation of the lateral ventricles. Homozygous variants in the more proximal exons of KIDINS220 have been reported in several fetuses with a similar but more severe phenotype of limb contractures and severe ventriculomegaly identified in the second trimester of pregnancy.

Case Presentation

We present here a 2.5-year-old female with profound global developmental delays and spasticity who was found by fetal ultrasound in week 19 of gestation to have bilateral talipes equinovarus and severe bilateral ventriculomegaly. Postnatal genetic testing revealed biallelic variants in KIDINS220.

Discussion

To our knowledge, this is the first living individual reported with the autosomal recessive form of a KIDINS220-associated condition. This case provides additional information about the postnatal phenotype and a detailed history of development from prenatal ultrasonography.

Functional analysis of a novel fusion protein PAX5-KIDINS220 identified in a pediatric Ph-like ALL patient

PAX5-KIDINS220 (PAX5-K220) is a novel chimeric fusion gene identified in a pediatric Philadelphia chromosome (Ph)-like acute lymphoblastic leukemia (ALL) patient, but the function of the encoded fusion protein has not yet been analyzed. Here, we report the functional analysis of PAX5-K220 in vitro. We successfully generated PAX5-K220 expressing cells and demonstrate that PAX5-K220 is a nuclear protein. Luciferase reporter assay reveals that PAX5-K220 inhibits wild-type PAX5 transcriptional activity in a dominant-negative fashion like other PAX5-related fusion proteins, and may contribute to lymphocyte differentiation block. However, although identified in Ph-like ALL, PAX5-K220 does not induce IL-3-independent proliferation when transduced in the IL-3-dependent Ba/F3 murine leukemia cells, but rather attenuates growth. These results reveal that PAX5-K220 certainly shares the character with other PAX5-related fusion proteins rather than other fusion proteins with tyrosine kinase activity identified in Ph-like ALL, and did not contribute to proliferation activity. Precise functional analysis of each differently partnered PAX5 fusion protein is warranted in the future for better understanding of PAX5-related translocations and their effects.