Pyloric Stenosis in a Patient with CEDNIK Syndrome.

We present a rare neurocutaneous genetic disorder where patients develop a combination of cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma, commonly known as CEDNIK syndrome. It is an autosomal recessive inheritance involving the SNAP29 protein, mapped to the 22q11.2 gene. Phenotypic variation is seen with this disease, with clinical manifestation of developmental milestone delays ranging in severity. With only a handful of documented cases, available research, management of the syndrome, and prognosis are not well established. As CEDNIK syndrome has systemic implications, care coordination between specialists is essential in improving patient outcomes. Particularly important is preventing patients from meeting the criteria of failure to thrive, a commonly reported issue. In this case, we present a four-month-old male with a past medical history of pyloric stenosis status/post pyloromyotomy who has failure to thrive, gastroesophageal reflux disease, profound hypotonia, and delayed progression of developmental milestones. Additionally, the case is complicated by idiopathic pyloric stenosis, further contributing to the patient's failure to thrive. We aim to discuss the pathophysiology of this syndrome, explore the timeline of disease progression, as well as compare our case to the current literature.

Snapshots from within the cell: Novel trafficking and non trafficking functions of Snap29 during tissue morphogenesis.

Membrane trafficking is a core cellular process that supports diversification of cell shapes and behaviors relevant to morphogenesis during development and in adult organisms. However, how precisely trafficking components regulate specific differentiation programs is incompletely understood. Snap29 is a multifaceted Soluble N-ethylmaleimide-sensitive factor Attachment protein Receptor, involved in a wide range of trafficking and non-trafficking processes in most cells. A body of knowledge, accrued over more than two decades since its discovery, reveals that Snap29 is essential for establishing and maintaining the operation of a number of cellular events that support cell polarity and signaling. In this review, we first summarize established functions of Snap29 and then we focus on novel ones in the context of autophagy, Golgi trafficking and vesicle fusion at the plasma membrane, as well as on non-trafficking activities of Snap29. We further describe emerging evidence regarding the compartmentalisation and regulation of Snap29. Finally, we explore how the loss of distinct functions of human Snap29 may lead to the clinical manifestations of congenital disorders such as CEDNIK syndrome and how altered SNAP29 activity may contribute to the pathogenesis of cancer, viral infection and neurodegenerative diseases.

CEDNIK syndrome with phenotypic variability.

CEDNIK syndrome is a rare autosomal recessive syndrome characterized by cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma of which 25 cases from 19 families have been reported to date. It is a progressive neurodegenerative disorder caused by the loss-of-function pathogenic variant of the SNAP29 gene encoding a member of the SNARE family of proteins. We describe two female siblings from a Syrian parent-related family with CEDNIK syndrome due to homozygous pathogenic variant in SNAP29 [c.223delG(p.Val75Serf*28)]. Palmoplantar keratoderma, reported as a cardinal sign in CEDNIK syndrome, was absent in both patients as of the last follow-up, and one of our patients had a verrucous venous malformation, a finding that has not been previously reported.

CEDNIK syndrome in a Brazilian patient with compound heterozygous pathogenic variants.

CEDNIK (Cerebral Dysgenesis, Neuropathy, Ichthyosis, and Keratoderma) syndrome is a neuro ichthyotic syndrome characterized by a clinical constellation of features including severe developmental delay, microcephaly, and facial dysmorphism. Here, we report the clinical and molecular characterization of a patient with CEDNIK syndrome harboring two compound heterozygous variants in the SNAP29 gene. The patient presents a combination of a loss-of-function SNAP29 mutation and a ∼370 kb 22q11.2 deletion, each of these genetic variants inherited from one of the parents. This report provides detailed data of a patient with unprecedented genetic events leading to the CEDNIK phenotype and may contribute to the elucidation of this rare condition.

Analysis of clinical phenotype and genotype of cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma syndrome caused by a novel variant of SNAP29 gene / 中华神经科杂志

Objective:To investigate the clinial phenotype and genetic characteristics of a child with cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma (CEDNIK) syndrome and to improve the clinicians′ understanding of this disease.Methods:Clinical data of the child with CEDNIK syndrome diagnosed in Department of Endocrinology, Genetics and Metabolism, Xi′an Children′s Hospital in June 2020 were collected. Whole exome sequencing was carried out to identify the potential variants of SNAP29 gene. Suspected variants were verified by Sanger sequencing of family numbers. The literature about the cases of CEDNIK syndrome were reviewed.Results:The proband is a boy, who was aged 1 year and 4 months, had the manifestations of psychomotor retardation, microcephaly, feeding difficulties, severe malnutrition, recurrent respiratory tract infection, binocular esotropia, sensorineural deafness, cutaneous ichthyosis and keratosis, left cryptorchidism. Brain magnetic resonance imaging indicated congenital dysplasia. Whole exome sequencing identified a homozygous variant of c.383dupT (p.E129Rfs *5) in the SNAP29 gene of the proband, and the heterozygous variation was observed at the same locus in his parents, which conformed to the autosomal recessive inheritance. This mutataion was determined as a pathogenic mutation according to the guidelines of American College of Medical Genetics and Genomics. Literature retrieval showed currently a total of 29 cases of CEDNIK syndrome were reported, containing 8 types of SNAP29 gene mutation. However, there was no Chinese case reported. And the c.383dupT (p.E129Rfs *5) mutation found in this study was a novel one which had not been reported yet. Conclusion:The phenotype of the proband is generally consistent with the CEDNIK syndrome and the novel c.383dupT (p.E129Rfs *5) mutation of SNAP29 gene is the genetic cause.

Generation and Characterization of a CRISPR/Cas9-Mediated SNAP29 Knockout in Human Fibroblasts.

Loss-of-function mutations in the synaptosomal-associated protein 29 (SNAP29) lead to the rare autosomal recessive neurocutaneous cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma (CEDNIK) syndrome. SNAP29 is a soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein. So far, it has been shown to be involved in membrane fusion, epidermal differentiation, formation of primary cilia, and autophagy. Recently, we reported the successful generation of two mouse models for the human CEDNIK syndrome. The aim of this investigation was the generation of a CRISPR/Cas9-mediated SNAP29 knockout (KO) in an immortalized human cell line to further investigate the role of SNAP29 in cellular homeostasis and signaling in humans independently of animal models. Comparison of different methods of delivery for CRISPR/Cas9 plasmids into the cell revealed that lentiviral transduction is more efficient than transfection methods. Here, we reported to the best of our knowledge the first successful generation of a CRISPR/Cas9-mediated SNAP29 KO in immortalized human MRC5Vi fibroblasts (c.169_196delinsTTCGT) via lentiviral transduction.

NEK3-mediated SNAP29 phosphorylation modulates its membrane association and SNARE fusion dependent processes.

Intracellular membrane fusion depends on the presence of specific mediators, the vesicle (v-) and the target (t-) SNAREs (Soluble N-ethylmaleimide-sensitive factor, NSF, attachment protein SNAP receptors), whose interaction brings apposing membranes to close proximity and initiates their fusion. SNAP29 (synaptosomal-associated protein 29), a t-SNARE protein, is involved in multiple fusion events during intracellular transport and affects structure of organelles such as the Golgi apparatus and focal adhesions. Mutations in SNAP29 gene result in CEDNIK (Cerebral dysgenesis, neuropathy, ichthyosis and palmoplantar keratoderma) syndrome. In the present study, we show that NEK3 (NIMA-never in mitosis gene A-related kinase 3)-mediated serine 105 (S105) phosphorylation of SNAP29 directs its membrane association, without which cells present defective focal adhesion formation, impaired Golgi structure and attenuated cellular recycling. In contrast to a phosphorylation-defective serine 105 to alanine (S105A) mutant, wildtype SNAP29, partially rescued the abnormal morphology of a CEDNIK patient derived fibroblasts. Our results highlight the importance of NEK3-mediated S105 phosphorylation of SNAP29 for its membrane localization and for membrane fusion dependent processes.

CEDNIK: Phenotypic and Molecular Characterization of an Additional Patient and Review of the Literature.

Synaptosomal-associated protein 29 (SNAP29) is a t-SNARE protein that is implicated in intracellular vesicle fusion. Mutations in the SNAP29 gene have been associated with cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma syndrome (CEDNIK). In patients with 22q11.2 deletion syndrome, mutations in SNAP29 on the nondeleted chromosome are linked to similar ichthyotic and neurological phenotypes. Here, the authors report a patient with cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma syndrome who presented with global developmental delay, polymicrogyria, dysgenesis of the corpus callosum, optic nerve dysplasia, gaze apraxia, and dysmorphic features. He has developed ichthyosis and palmoplantar keratoderma as he has grown. Exome sequencing identified a homozygous nonsense mutation in SNAP29 gene designated as c.85C>T (p.Arg29X). The authors compare the findings in the proband with previously reported cases. The previously unreported mutation in this patient and his phenotype add to the characterization of cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma syndrome and the accumulating scientific evidence that implicates synaptic protein dysfunction in various neuroectodermal conditions.

Multiple functions of the SNARE protein Snap29 in autophagy, endocytic, and exocytic trafficking during epithelial formation in Drosophila.

How autophagic degradation is linked to endosomal trafficking routes is little known. Here we screened a collection of uncharacterized Drosophila mutants affecting membrane transport to identify new genes that also have a role in autophagy. We isolated a loss of function mutant in Snap29 (Synaptosomal-associated protein 29 kDa), the gene encoding the Drosophila homolog of the human protein SNAP29 and have characterized its function in vivo. Snap29 contains 2 soluble NSF attachment protein receptor (SNARE) domains and a asparagine-proline-phenylalanine (NPF motif) at its N terminus and rescue experiments indicate that both SNARE domains are required for function, whereas the NPF motif is in part dispensable. We find that Snap29 interacts with SNARE proteins, localizes to multiple trafficking organelles, and is required for protein trafficking and for proper Golgi apparatus morphology. Developing tissue lacking Snap29 displays distinctive epithelial architecture defects and accumulates large amounts of autophagosomes, highlighting a major role of Snap29 in autophagy and secretion. Mutants for autophagy genes do not display epithelial architecture or secretion defects, suggesting that the these alterations of the Snap29 mutant are unlikely to be caused by the impairment of autophagy. In contrast, we find evidence of elevated levels of hop-Stat92E (hopscotch-signal transducer and activator of transcription protein at 92E) ligand, receptor, and associated signaling, which might underlie the epithelial defects. In summary, our findings support a role of Snap29 at key steps of membrane trafficking, and predict that signaling defects may contribute to the pathogenesis of cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma (CEDNIK), a human congenital syndrome due to loss of Snap29.