Hereditary spastic paraplegia caused by compound heterozygous mutations outside the motor domain of the KIF1A gene

Cryo-EM Unveils the Processivity Mechanism of Kinesin KIF1A and the Impact of its Pathogenic Variant P305L

Mutations in the microtubule-associated motor protein KIF1A lead to severe neurological conditions known as KIF1A-associated neurological disorders (KAND). Despite insights into its molecular mechanism, high-resolution structures of KIF1A-microtubule complexes remain undefined. Here, we present 2.7-3.4 Å resolution structures of dimeric microtubule-bound KIF1A, including the pathogenic P305L mutant, across various nucleotide states. Our structures reveal that KIF1A binds microtubules in one- and two-heads-bound configurations, with both heads exhibiting distinct conformations with tight inter-head connection. Notably, KIF1A's class-specific loop 12 (K-loop) forms electrostatic interactions with the C-terminal tails of both α- and β-tubulin. The P305L mutation does not disrupt these interactions but alters loop-12's conformation, impairing strong microtubule-binding. Structure-function analysis reveals the K-loop and head-head coordination as major determinants of KIF1A's superprocessive motility. Our findings advance the understanding of KIF1A's molecular mechanism and provide a basis for developing structure-guided therapeutics against KAND.

Expanding the Knowledge of KIF1A-Dependent Disorders to a Group of Polish Patients

BACKGROUND

KIF1A (kinesin family member 1A)-related disorders encompass a variety of diseases. KIF1A variants are responsible for autosomal recessive and dominant spastic paraplegia 30 (SPG, OMIM610357), autosomal recessive hereditary sensory and autonomic neuropathy type 2 (HSN2C, OMIM614213), and autosomal dominant neurodegeneration and spasticity with or without cerebellar atrophy or cortical visual impairment (NESCAV syndrome), formerly named mental retardation type 9 (MRD9) (OMIM614255). KIF1A variants have also been occasionally linked with progressive encephalopathy with brain atrophy, progressive neurodegeneration, PEHO-like syndrome (progressive encephalopathy with edema, hypsarrhythmia, optic atrophy), and Rett-like syndrome.

MATERIALS AND METHODS

The first Polish patients with confirmed heterozygous pathogenic and potentially pathogenic KIF1A variants were analyzed. All the patients were of Caucasian origin. Five patients were females, and four were males (female-to-male ratio = 1.25). The age of onset of the disease ranged from 6 weeks to 2 years.

RESULTS

Exome sequencing identified three novel variants. Variant c.442G>A was described in the ClinVar database as likely pathogenic. The other two novel variants, c.609G>C; p.(Arg203Ser) and c.218T>G, p.(Val73Gly), were not recorded in ClinVar.

CONCLUSIONS

The authors underlined the difficulties in classifying particular syndromes due to non-specific and overlapping signs and symptoms, sometimes observed only temporarily.

Identification of an in-frame homozygous KIF1A variant causing a mild SPG30 phenotype in a Korean family

SPG30 is a newly categorized type of HSP caused by variants in the kinesin family member 1A gene (KIF1A). Advances in next-generation sequencing have resulted in a limited number of studies describing the clinical, electrophysiological, and radiological features of HSP, with variable manifestations. Most known pathogenic KIF1A variants affect the motor domain, although some rare pathogenic variants have been identified that affect the non-motor domain. Here, we report a Korean family with a rare homozygous autosomal-recessive form of SPG30. A 59-year-old man and his father presented with an uncomplicated, mild SPG30 phenotype, characterized by a progressive, spastic gait. Familial co-segregation analysis revealed a pathogenic c.2751_2753delGGA KIF1A variant that affects the non-motor domain. Our case broadens the genetic and clinical variability of SPG30, warranting similar studies to consolidate the pathogenicity of SPG30.

Positive charge in the K-loop of the kinesin-3 motor KIF1A regulates superprocessivity by enhancing microtubule affinity in the one-head-bound state

KIF1A is an essential neuronal transport motor protein in the kinesin-3 family, known for its superprocessive motility. However, structural features underlying this function are unclear. Here, we determined that superprocessivity of KIF1A dimers originates from a unique structural domain, the lysine-rich insertion in loop-12 termed the 'K-loop', which enhances electrostatic interactions between the motor and the microtubule. In 80 mM PIPES buffer, replacing the native KIF1A loop-12 with that of kinesin-1 resulted in a 6-fold decrease in run length, whereas adding additional positive charge to loop-12 enhanced the run length. Interestingly, swapping the KIF1A loop-12 into kinesin-1 did not enhance its run length, consistent with the two motor families using different mechanochemical tuning to achieve persistent transport. To investigate the mechanism by which the KIF1A K-loop enhances processivity, we used microtubule pelleting and single-molecule dwell time assays in ATP and ADP. First, the microtubule affinity was similar in ATP and in ADP, consistent with the motor spending the majority of its cycle in a weakly bound state. Second, the microtubule affinity and single-molecule dwell time in ADP were 6-fold lower in the loop-swap mutant than WT. Thus, the positive charge in loop-12 of KIF1A enhances the run length by stabilizing binding of the motor in its vulnerable one-head-bound state. Finally, through a series of mutants with varying positive charge in the K-loop, we found that KIF1A processivity is linearly dependent on the charge of loop-12, further highlighting how loop-12 contributes to the function of this key motor protein.

Single-Molecule Studies on the Motion and Force Generation of the Kinesin-3 Motor KIF1A

KIF1A is a neuron-specific member of the kinesin-3 family of microtubule (MT) plus-end-directed motor proteins. It powers the migration of nuclei in differentiating brain stem cells and the transport of synaptic precursors and dense core vesicles in axons. Its dysfunction causes severe neurodevelopmental and neurodegenerative diseases termed KIF1A-associated neurological disorders (KAND). KAND mutations span the entirety of the KIF1A protein sequence, of which the majority are located within the motor domain and are thus predicted to affect the motor's motility and force-generating properties. Unfortunately, the molecular etiologies of KAND remain poorly understood, in part because KIF1A's molecular mechanism remains unclear. Here, we describe detailed methods for how to express a tail-truncated dimeric KIF1A in E. coli cells and provide step-by-step protocols for performing single-molecule studies with total internal reflection fluorescence microscopy and optical tweezers assays, which, when combined with structure-function studies, help to decipher KIF1A's molecular mechanism.

Monoallelic KIF1A-related disorders: a multicenter cross sectional study and systematic literature review

BACKGROUND

Monoallelic variants in the KIF1A gene are associated with a large set of clinical phenotypes including neurodevelopmental and neurodegenerative disorders, underpinned by a broad spectrum of central and peripheral nervous system involvement.

METHODS

In a multicenter study conducted in patients presenting spastic gait or complex neurodevelopmental disorders, we analyzed the clinical, genetic and neuroradiological features of 28 index cases harboring heterozygous variants in KIF1A. We conducted a literature systematic review with the aim to comparing our findings with previously reported KIF1A-related phenotypes.

RESULTS

Among 28 patients, we identified nine novel monoallelic variants, and one a copy number variation encompassing KIF1A. Mutations arose de novo in most patients and were prevalently located in the motor domain. Most patients presented features of a continuum ataxia-spasticity spectrum with only five cases showing a prevalently pure spastic phenotype and six presenting congenital ataxias. Seventeen mutations occurred in the motor domain of the Kinesin-1A protein, but location of mutation did not correlate with neurological and imaging presentations. When tested in 15 patients, muscle biopsy showed oxidative metabolism alterations (6 cases), impaired respiratory chain complexes II + III activity (3/6) and low CoQ10 levels (6/9). Ubiquinol supplementation (1gr/die) was used in 6 patients with subjective benefit.

CONCLUSIONS

This study broadened our clinical, genetic, and neuroimaging knowledge of KIF1A-related disorders. Although highly heterogeneous, it seems that manifestations of ataxia-spasticity spectrum disorders seem to occur in most patients. Some patients also present secondary impairment of oxidative metabolism; in this subset, ubiquinol supplementation therapy might be appropriate.

Genotype and defects in microtubule-based motility correlate with clinical severity in KIF1A-associated neurological disorder

KIF1A-associated neurological disorder (KAND) encompasses a group of rare neurodegenerative conditions caused by variants in KIF1A,a gene that encodes an anterograde neuronal microtubule (MT) motor protein. Here we characterize the natural history of KAND in 117 individuals using a combination of caregiver or self-reported medical history, a standardized measure of adaptive behavior, clinical records, and neuropathology. We developed a heuristic severity score using a weighted sum of common symptoms to assess disease severity. Focusing on 100 individuals, we compared the average clinical severity score for each variant with in silico predictions of deleteriousness and location in the protein. We found increased severity is strongly associated with variants occurring in protein regions involved with ATP and MT binding: the P loop, switch I, and switch II. For a subset of variants, we generated recombinant proteins, which we used to assess transport in vivo by assessing neurite tip accumulation and to assess MT binding, motor velocity, and processivity using total internal reflection fluorescence microscopy. We find all modeled variants result in defects in protein transport, and we describe three classes of protein dysfunction: reduced MT binding, reduced velocity and processivity, and increased non-motile rigor MT binding. The rigor phenotype is consistently associated with the most severe clinical phenotype, while reduced MT binding is associated with milder clinical phenotypes. Our findings suggest the clinical phenotypic heterogeneity in KAND likely reflects and parallels diverse molecular phenotypes. We propose a different way to describe KAND subtypes to better capture the breadth of disease severity.

Clinical and molecular characterization of hereditary spastic paraplegia in a spanish southern region

Spastic paraplegia (SPG) is a syndrome characterised by lower limb spasticity, occurring alone or in association with other neurological manifestations. Despite of the new molecular technologies, many patients remain yet undiagnosed. The purpose of this study was to describe the clinical presentation and molecular characteristics of a cohort of 27 patients from 18 different families with SPG in the south of Spain. We used a targeted next-generation sequencing (NGS) approach to study a proband from each family. Variants in SPG11 gene were the most common cause of SPG in our area. We made a genetic diagnosis in 52% of cases, identified 3 novel variants and reclassified one uncertain variant in SPG11 gene as pathogenic variant. We identified a patient with two truncanting mutation in SPG11 gene and late onset disease and report another missense mutation outside of motor domain of KIF1A gene in a family with pure SPG. Our study contributes to enhance the scientific knowledge of SPG. It is important to note the large group of cases (48%) that were not genetically diagnosed in our cohort. Therefore NGS approach is an efficient diagnostic tool, but it still large the number of non-diagnosed subjects, suggesting further genetic heterogeneity.

KIF1A-related autosomal dominant spastic paraplegias (SPG30) in Russian families

Background

Spastic paraplegia type 30 (SPG30) caused by KIF1A mutations was first reported in 2011 and was initially considered a very rare autosomal recessive (AR) form. In the last years, thanks to the development of massive parallel sequencing, SPG30 proved to be a rather common autosomal dominant (AD) form of familial or sporadic spastic paraplegia (SPG),, with a wide range of phenotypes: pure and complicated. The aim of our study is to detect AD SPG30 cases and to examine their molecular and clinical characteristics for the first time in the Russian population.

Methods

Clinical, genealogical and molecular methods were used. Molecular methods included massive parallel sequencing (MPS) of custom panel ‘spastic paraplegias’ with 62 target genes complemented by familial Sanger sequencing. One case was detected by the whole -exome sequencing.

Results

AD SPG30 was detected in 10 unrelated families, making it the 3rd (8.4%) most common SPG form in the cohort of 118 families. No AR SPG30 cases were detected. In total, 9 heterozygous KIF1A mutations were detected, with 4 novel and 5 known mutations. All the mutations were located within KIF1A motor domain. Six cases had pure phenotypes, of which 5 were familial, where 2 familial cases demonstrated incomplete penetrance, early onset and slow relatively benign SPG course. All 4 complicated cases were caused by novel mutations without familial history. The phenotypes varied from severe in two patients (e.g. lack of walking, pronounced mental retardation) to relatively mild non-disabling symptoms in two others.

Conclusion

AD SPG30 is one of the most common forms of SPG in Russia, the disorder has pronounced clinical variability while pure familial cases represent a significant part.

Heterozygous KIF1A variants underlie a wide spectrum of neurodevelopmental and neurodegenerative disorders

BACKGROUND

Dominant and recessive variants in the KIF1A gene on chromosome 2q37.3 are associated with several phenotypes, although only three syndromes are currently listed in the OMIM classification: hereditary sensory and autonomic neuropathy type 2 and spastic paraplegia type 30, both recessively inherited, and mental retardation type 9 with dominant inheritance.

METHODS

In this retrospective multicentre study, we describe the clinical, neuroradiological and genetic features of 19 Caucasian patients (aged 3-65 years) harbouring heterozygous KIF1A variants, and extensively review the available literature to improve current classification of KIF1A-related disorders.

RESULTS

Patients were divided into two groups. Group 1 comprised patients with a complex phenotype with prominent pyramidal signs, variably associated in all but one case with additional features (ie, epilepsy, ataxia, peripheral neuropathy, optic nerve atrophy); conversely, patients in group 2 presented an early onset or congenital ataxic phenotype. Fourteen different heterozygous missense variants were detected by next-generation sequencing screening, including three novel variants, most falling within the kinesin motor domain.

CONCLUSION

The present study further enlarges the clinical and mutational spectrum of KIF1A-related disorders by describing a large series of patients with dominantly inherited KIF1A pathogenic variants ranging from pure to complex forms of hereditary spastic paraparesis/paraplegias (HSP) and ataxic phenotypes in a lower proportion of cases. A comprehensive review of the literature indicates that KIF1A screening should be implemented in HSP regardless of its mode of inheritance or presentations as well as in other complex neurodegenerative or neurodevelopmental disorders showing congenital or early onset ataxia.

Expansion of the phenotypic spectrum of de novo missense variants in kinesin family member 1A (KIF1A)

Defects in the motor domain of kinesin family member 1A (KIF1A), a neuron-specific ATP-dependent anterograde axonal transporter of synaptic cargo, are well-recognized to cause a spectrum of neurological conditions, commonly known as KIF1A-associated neurological disorders (KAND). Here, we report one mutation-negative female with classic Rett syndrome (RTT) harboring a de novo heterozygous novel variant [NP_001230937.1:p.(Asp248Glu)] in the highly conserved motor domain of KIF1A. In addition, three individuals with severe neurodevelopmental disorder along with clinical features overlapping with KAND are also reported carrying de novo heterozygous novel [NP_001230937.1:p.(Cys92Arg) and p.(Pro305Leu)] or previously reported [NP_001230937.1:p.(Thr99Met)] variants in KIF1A. In silico tools predicted these variants to be likely pathogenic, and 3D molecular modeling predicted defective ATP hydrolysis and/or microtubule binding. Using the neurite tip accumulation assay, we demonstrated that all novel KIF1A variants significantly reduced the ability of the motor domain of KIF1A to accumulate along the neurite lengths of differentiated SH-SY5Y cells. In vitro microtubule gliding assays showed significantly reduced velocities for the variant p.(Asp248Glu) and reduced microtubule binding for the p.(Cys92Arg) and p.(Pro305Leu) variants, suggesting a decreased ability of KIF1A to move along microtubules. Thus, this study further expanded the phenotypic characteristics of KAND individuals with pathogenic variants in the KIF1A motor domain to include clinical features commonly seen in RTT individuals.

KIF1A-related disorders in children: A wide spectrum of central and peripheral nervous system involvement

KIF1A-related disorders (KRD) were first described in 2011 and the phenotypic spectrum has subsequently expanded to encompass a range of central and peripheral nervous system involvement. Here we present a case series demonstrating the range of clinical, neurophysiological, and radiological features which may occur in childhood-onset KRD. We report on all the children and young people seen at a single large tertiary centre. Data were collected through a retrospective case-notes review. Twelve individuals from 10 families were identified. Eight different mutations were present, including four novel mutations. Two patients displayed a very severe phenotype including congenital contractures, severe spasticity and/or dystonia, dysautonomia, severe sensorimotor polyneuropathy and optic atrophy, significant white matter changes on brain MRI, respiratory insufficiency, and complete lack of neurodevelopmental progress. The remaining 10 patients represented a spectrum of severity with common features including a movement disorder with spasticity and/or dystonia, subtle features of dysautonomia, sensory axonal neuropathy, varying degrees of optic atrophy and of learning and/or behavioural difficulties, and subtle or absent-but sometimes progressive-changes in white matter on MRI. Epilepsy was common among the more severely affected children. This case series demonstrates that KRD comprise a range of neurological disorders, with both the milder and the more severe forms combining central and peripheral (including autonomic) nervous system deficits.

Generation of a human induced pluripotent stem cell line (SDUBMSi001-A) from a hereditary spastic paraplegia patient carrying kif1a c.773C>T missense mutation

KIF1A gene encodes the kinesin 1a protein, an axonal motor protein participating in axonal transport. Variants in KIF1A were identified in different forms of neurodegenerative diseases. Here, we generated induced pluripotent stem cells (iPSCs) from a Chinese hereditary spastic paraplegia (HSP) patient carrying a compound heterozygous c.773C>T(p.T258M) mutation in KIF1A gene by reprogramming peripheral blood cells with non-integrative vectors. The generated iPSC line (SDUBMSi001-A) had a normal karyotype, expressed pluripotency markers and could be differentiated into three germ layers in vitro.

Overlapping spectrums: The clinicogenetic commonalities between Charcot-Marie-Tooth and other neurodegenerative diseases

Charcot-Marie-Tooth (CMT) disease is a progressive and heterogeneous inherited peripheral neuropathy. A myriad of genetic factors have been identified that contribute to the degeneration of motor and sensory axons in a length-dependent manner. Emerging biological themes underlying disease include defects in axonal trafficking, dysfunction in RNA metabolism and protein homeostasis, as well deficits in the cellular stress response. Moreover, genetic contributions to CMT can have overlap with other neuropathies, motor neuron diseases (MNDs) and neurodegenerative disorders. Recent progress in understanding the molecular biology of CMT and overlapping syndromes aids in the search for necessary therapeutic targets.

Long-term follow-up until early adulthood in autosomal dominant, complex SPG30 with a novel KIF1A variant: a case report

BACKGROUND

Pathogenic variants in KIF1A (kinesin family member 1A) gene have been associated with hereditary spastic paraplegia (HSP) type 30 (SPG30), encopassing autosomal dominant and recessive, pure and complicated forms.

CASE PRESENTATION

We report the long-term follow-up of a 19 years-old boy first evaluated at 18 months of age because of toe walking and unstable gait with frequent falls. He developed speech delay, mild intellectual disability, a slowly progressive pyramidal syndrome, microcephaly, bilateral optic subatrophy and a sensory axonal polyneuropathy. Brain MRI showed cerebellar atrophy, stable along serial evaluations (last performed at 18 years of age). Targeted NGS sequencing disclosed the de novo c.914C > T missense, likely pathogenic variant on KIF1A gene.

CONCLUSIONS

We report on a previously unpublished de novo heterozygous likely pathogenic KIF1A variant associated with slowly progressive complicated SPG30 and stable cerebellar atrophy on long-term follow-up, adding to current knowledge on this HSP subtype.

Going Too Far Is the Same as Falling Short†: Kinesin-3 Family Members in Hereditary Spastic Paraplegia

Proper intracellular trafficking is essential for neuronal development and function, and when any aspect of this process is dysregulated, the resulting "transportopathy" causes neurological disorders. Hereditary spastic paraplegias (HSPs) are a family of such diseases attributed to over 80 spastic gait genes (SPG), specifically characterized by lower extremity spasticity and weakness. Multiple genes in the trafficking pathway such as those relating to microtubule structure and function and organelle biogenesis are representative disease loci. Microtubule motor proteins, or kinesins, are also causal in HSP, specifically mutations in Kinesin-I/KIF5A (SPG10) and two kinesin-3 family members; KIF1A (SPG30) and KIF1C (SPG58). KIF1A is a motor enriched in neurons, and involved in the anterograde transport of a variety of vesicles that contribute to pre- and post-synaptic assembly, autophagic processes, and neuron survival. KIF1C is ubiquitously expressed and, in addition to anterograde cargo transport, also functions in retrograde transport between the Golgi and the endoplasmic reticulum. Only a handful of KIF1C cargos have been identified; however, many have crucial roles such as neuronal differentiation, outgrowth, plasticity and survival. HSP-related kinesin-3 mutants are characterized mainly as loss-of-function resulting in deficits in motility, regulation, and cargo binding. Gain-of-function mutants are also seen, and are characterized by increased microtubule-on rates and hypermotility. Both sets of mutations ultimately result in misdelivery of critical cargos within the neuron. This likely leads to deleterious cell biological cascades that likely underlie or contribute to HSP clinical pathology and ultimately, symptomology. Due to the paucity of histopathological or cell biological data assessing perturbations in cargo localization, it has been difficult to positively link these mutations to the outcomes seen in HSPs. Ultimately, the goal of this review is to encourage future academic and clinical efforts to focus on "transportopathies" through a cargo-centric lens.

KIF1A variants are a frequent cause of autosomal dominant hereditary spastic paraplegia

Variants in the KIF1A gene can cause autosomal recessive spastic paraplegia 30, autosomal recessive hereditary sensory neuropathy, or autosomal (de novo) dominant mental retardation type 9. More recently, variants in KIF1A have also been described in a few cases with autosomal dominant spastic paraplegia. Here, we describe 20 KIF1A variants in 24 patients from a clinical exome sequencing cohort of 347 individuals with a mostly ‘pure’ spastic paraplegia. In these patients, spastic paraplegia was slowly progressive and mostly pure, but with a highly variable disease onset (0–57 years). Segregation analyses showed a de novo occurrence in seven cases, and a dominant inheritance pattern in 11 families. The motor domain of KIF1A is a hotspot for disease causing variants in autosomal dominant spastic paraplegia, similar to mental retardation type 9 and recessive spastic paraplegia type 30. However, unlike these allelic disorders, dominant spastic paraplegia was also caused by loss-of-function variants outside this domain in six families. Finally, three missense variants were outside the motor domain and need further characterization. In conclusion, KIF1A variants are a frequent cause of autosomal dominant spastic paraplegia in our cohort (6–7%). The identification of KIF1A loss-of-function variants suggests haploinsufficiency as a possible mechanism in autosomal dominant spastic paraplegia.

Next-generation sequencing study reveals the broader variant spectrum of hereditary spastic paraplegia and related phenotypes

Hereditary spastic paraplegias (HSPs) are clinically and genetically heterogeneous neurodegenerative disorders. Numerous genes linked to HSPs, overlapping phenotypes between HSP subtypes and other neurodegenerative disorders and the HSPs’ dual mode of inheritance (both dominant and recessive) make the genetic diagnosis of HSPs complex and difficult. Out of the original HSP cohort comprising 306 index cases (familial and isolated) who had been tested according to “traditional workflow/guidelines” by Multiplex Ligation-dependent Probe Amplification (MLPA) and Sanger sequencing, 30 unrelated patients (all familial cases) with unsolved genetic diagnoses were tested using next-generation sequencing (NGS). One hundred thirty-two genes associated with spastic paraplegias, hereditary ataxias and related movement disorders were analysed using the Illumina TruSight™ One Sequencing Panel. The targeted NGS data showed pathogenic variants, likely pathogenic variants and those of uncertain significance (VUS) in the following genes: SPAST (spastin, SPG4), ATL1 (atlastin 1, SPG3), WASHC5 (SPG8), KIF5A (SPG10), KIF1A (SPG30), SPG11 (spatacsin), CYP27A1, SETX and ITPR1. Out of the nine genes mentioned above, three have not been directly associated with the HSP phenotype to date. Considering the phenotypic overlap and joint cellular pathways of the HSP, spinocerebellar ataxia (SCA) and amyotrophic lateral sclerosis (ALS) genes, our findings provide further evidence that common genetic testing may improve the diagnostics of movement disorders with a spectrum of ataxia-spasticity signs.

Neuroprotection Exerted by Netrin-1 and Kinesin Motor KIF1A in Secondary Brain Injury following Experimental Intracerebral Hemorrhage in Rats

Binding of extracellular netrin-1 to its receptors, deleted in colorectal cancer (DCC) and uncoordinated gene 5H2 (UNC5H2), inhibits apoptosis mediated by these receptors. A neuron-specific kinesin motor protein, KIF1A, has been shown to participate in netrin-1 secretion. This study aimed to identify the roles of netrin-1 and KIF1A in secondary brain injury after intracerebral hemorrhage (ICH) and the potential mechanisms. An autologous blood ICH model was established in adult male Sprague-Dawley rats, and cultured neurons were exposed to OxyHb to mimic ICH conditions in vitro. Mouse recombinant netrin-1, expression vectors encoding KIF1A, and KIF1A-specific siRNAs were administered intracerebroventricularly. After ICH, protein levels of netrin-1, DCC, and UNC5H2 increased, while protein levels of KIF1A decreased. Levels of UNC5H2 and DCC bound to netrin-1 increased after ICH but were significantly lower than the increase in total amount of protein. Administration of recombinant netrin-1 attenuated neuronal apoptosis and degeneration in ICH rats. Moreover, KIF1A overexpression increased concentrations of netrin-1 in cerebrospinal fluid and cell culture supernatant and exerted neuroprotective effects via netrin-1 and its receptor pathways. KIF1A plays a critical role in netrin-1 secretion by neurons. An increase in protein levels of netrin-1 may be a neuroprotective strategy after ICH. However, this process is almost completely abolished by ICH-induced loss of KIF1A. An exogenous increase of KIF1A may be a potential strategy for neuroprotection via the netrin-1 pathway.