A genetic model of CEDNIK syndrome in zebrafish highlights the role of the SNARE protein Snap29 in neuromotor and epidermal development

Valeria Mastrodonato,Galina Beznoussenko,Thomas Vaccari,Laura Ferrari,Gianluca Deflorian,Alexandre Mironov

doi:10.1038/s41598-018-37780-4

Valeria Mastrodonato, Galina Beznoussenko + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-37780-4

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Abstract

Homozygous mutations in SNAP29, encoding a SNARE protein mainly involved in membrane fusion, cause CEDNIK (Cerebral Dysgenesis, Neuropathy, Ichthyosis and Keratoderma), a rare congenital neurocutaneous syndrome associated with short life expectancy, whose pathogenesis is unclear. Here, we report the analysis of the first genetic model of CEDNIK in zebrafish. Strikingly, homozygous snap29 mutant larvae display CEDNIK-like features, such as microcephaly and skin defects. Consistent with Snap29 role in membrane fusion during autophagy, we observe accumulation of the autophagy markers p62 and LC3, and formation of aberrant multilamellar organelles and mitochondria. Importantly, we find high levels of apoptotic cell death during early development that might play a yet uncharacterized role in CEDNIK pathogenesis. Mutant larvae also display mouth opening problems, feeding impairment and swimming difficulties. These alterations correlate with defective trigeminal nerve formation and excess axonal branching. Since the paralog Snap25 is known to promote axonal branching, Snap29 might act in opposition with, or modulate Snap25 activity during neurodevelopment. Our vertebrate genetic model of CEDNIK extends the description in vivo of the multisystem defects due to loss of Snap29 and could provide the base to test compounds that might ameliorate traits of the disease.

Highlights

Despite the widespread use of Snap[29] in several trafficking and non-trafficking processes, complete loss of human Snap[29] (SNAP29) does not cause embryonic lethality
Snap[29] has been found to compete with α-SNAP for the binding with the SNARE complex formed by Snap[25], Syntaxin1A and VAMP2, inhibiting SNARE complex disassembly that is required for synaptic vesicles recycling
The position of reported nonsense mutations associated to CEDNIK10,12 introduce stop codons that are expected to lead to the production of proteins truncated respectively within the first SNARE domain and before the second SNARE domain (Fig. 1A)

Summary

Introduction

Despite the widespread use of Snap[29] in several trafficking and non-trafficking processes, complete loss of human Snap[29] (SNAP29) does not cause embryonic lethality. (CEDNIK; OMIM # 609528), a rare autosomal recessive syndrome characterized by congenital neurological and dermatological alterations. These include palmoplantar keratoderma and ichthyosis, microcephaly, neurogenic muscle atrophy, reduced peripheral nerve conduction, corpus callosum abnormalities and cortical dysplasia. Granules containing lipid and protein are transported from the Golgi apparatus to the surface of the epidermis, suggesting that trafficking supporting normal skin development and homeostasis might be defective in CEDNIK patients[15]. CEDNIK patients present severe nervous system development defects, including pachygyria, polymicrogyria and psychomotor retardation. The nature and consequences of loss of SNAP29 in nervous system development remain elusive. We have investigated in vivo the cellular, tissue and organismal consequences of lack of Snap[29] on vertebrate development. We report alteration of neuro-muscular development that might shed light on ill-explored aspects of CEDNIK

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