Griscelli syndrome type 1: a novel pathogenic variant, and review of literature.

Griscelli syndrome type 1 (GS1) is a rare inherited autosomal recessive disease caused by a deleterious variant in the MYO5A gene and characterized by general hypopigmentation, neurological symptoms, motor disability, hypotonia, and vision abnormality. Only nine pathogenic variants in the MYO5A gene have been confirmed in association with the GS1. All of the reported pathogenic variants are truncating. Herein, two siblings from a consanguineous Iranian family with abnormal pigmentation and neurological symptoms were referred for genetic counseling. Whole-exome sequencing (WES) revealed a novel homozygous truncating variant c.1633_1634delAA (p.Asn545Glnfs*10) in the MYO5A gene, which was completely co-segregated with the phenotype in all affected and unaffected family members. Computational analysis and protein modeling demonstrated the deleterious effects of this variant on the structure and function of the protein. The variant, according to ACMG guidelines, was classified as pathogenic. Besides the novelty of the identified variant, our patients manifested more severe clinical symptoms and presented distal hyperlaxity in all four limbs, which was a new finding. In conclusion, we expanded the mutational and phenotypic spectrum of the GS1. Moreover, by studying clinical manifestations in all molecularly confirmed reported cases, provided a comprehensive overview of clinical presentation, and attempted to find a genotype-phenotype correlation.

MYO5A overexpression promotes invasion and correlates with low lymphocyte infiltration in head and neck squamous carcinoma.

Head and neck squamous carcinoma (HNSC) poses a significant public health challenge due to its substantial morbidity. Nevertheless, despite advances in current treatments, the prognosis for HNSC remains unsatisfactory. To address this, single-cell RNA sequencing (RNA-seq) and bulk RNA-seq data combined with in vitro studies were conducted to examine the role of MYO5A (Myosin VA) in HNSC. Our investigation revealed an overexpression of MYO5A in HNSC that promotes HNSC migration in vitro. Remarkably, knockdown of MYO5A suppressed vimentin expression. Furthermore, analyzing the TCGA database evidenced that MYO5A is a risk factor for human papillomavirus positive (HPV+) HNSC (HR = 0.81, P < 0.001). In high MYO5A expression HNSC, there was a low count of tumor infiltrating lymphocytes (TIL), including activated CD4+ T cells, CD8+ T cells, and B cells. Of note, CD4+ T cells and B cells were positively associated with improved HPV+ HNSC outcomes. Correlation analysis demonstrated a decreased level of immunostimulators in high MYO5A-expressing HNSC. Collectively, these findings suggest that MYO5A may promote HNSC migration through vimentin and involve itself in the process of immune infiltration in HNSC, advancing the understanding of the mechanisms and treatment of HNSC.

Circ-FNDC3B Functions as an Oncogenic Factor in Esophageal Squamous Cell Carcinoma via Upregulating MYO5A by Absorbing miR-136-5p and miR-370-3p.

Circular RNAs (circRNAs) are a class of key regulators in cancers via regulating gene levels by acting as sponges of miRNAs. This study was devoted to explore the functional mechanism of circRNA fibronectin type III domain-containing protein 3B (circ-FNDC3B) in esophageal squamous cell carcinoma (ESCC). RNA levels were examined via reverse transcription-quantitative polymerase chain reaction assay. Cell viability detection was performed using Cell Counting Kit-8 assay. The proliferation ability was determined through colony formation assay and EDU assay. Flow cytometry was applied for analysis of apoptosis. Invasion ability was assessed via transwell assay. Target binding was analyzed by dual-luciferase reporter assay. The protein expression was measured using western blot. In vivo research was conducted via xenograft model in mice. Circ-FNDC3B exhibited significant upregulation in ESCC tissues and cells. Downregulation of circ-FNDC3B inhibited ESCC cell proliferation and invasion but accelerated cell apoptosis. Circ-FNDC3B interacted with miR-136-5p or miR-370-3p. The function of circ-FNDC3B was achieved by sponging miR-136-5p or miR-370-3p. Myosin VA (MYO5A) acted as a downstream target of miR-136-5p or miR-370-3p. MYO5A reversed miR-136-5p/miR-370-3p-induced tumor inhibition in ESCC cells. Circ-FNDC3B targeted miR-136-5p or miR-370-3p to affect MYO5A expression. Circ-FNDC3B knockdown reduced tumor growth in vivo by inhibiting miR-136-5p or miR-370-3p-mediated MYO5A expression. These findings demonstrated that circ-FNDC3B contributed to malignant progression of ESCC cells via miR-136-5p/MYO5A or miR-370-3p/MYO5A axis.

Novel mutations in the Myo5a gene cause a dilute coat color phenotype in mice.

C57BL/6 laboratory mice usually show black coat color. We observed a dilute (gray) coat color phenotype in progenies of two C57BL/6 mice. This phenotype is inherited in an autosomal recessive mode. To uncover the molecular mechanism underlying this naturally occurring phenotypic variation, we performed whole-genome sequencing (25×) on 10 offspring of the two founder mice. The whole-genome DNA sequencing and additional RNA-Seq data reveal that Myo5a is the gene responsible for the coat color dilution in C57BL/6 mice, and novel mutations in the Myo5a gene are likely causal. We further performed reverse transcription-quantitative PCR, and showed increased expression of truncated Myo5a transcripts encoding dysfunctional proteins and decreased expression of Myo5a full-length transcripts encoding functional proteins in mutant individuals. The decrease in full-length messenger RNA abundance was accompanied by reduced Myo5a protein level and deficient melanosome transport, a potential mechanistic link between the Myo5a mutations and the dilute color phenotype. This study not only advances our understanding of the molecular mechanisms of pigmentation in mice, but also provides a typical case of deciphering the molecular basis of phenotypic variation in mice by genomic analyses and subsequent functional work.

LINC01980 facilitates esophageal squamous cell carcinoma progression via regulation of miR-190a-5p/MYO5A pathway.

Understanding the role of Long non-coding RNAs (lncRNAs) in tumorigenesis in diverse human malignancies would helpful for targeted therapies, containing esophageal squamous cell carcinoma (ESCC). However, the specific role and molecular mechanisms of LINC01980 in ESCC remain unclarified. In this study, we investigated the expression level, function role, and molecular mechanisms of LINC01980 in esophageal cancer cells and ESCC tissues. The high expression of LINC01980 was detected in ESCC tissues and cells, and predicted poor prognosis. LINC01980 promoted the cell proliferation, migration, invasion ability and epithelial-mesenchymal transition (EMT) progress in ESCC cells. In addition, a negative correlation between LINC01980 and miR-190a-5p or miR-190a-5p and MYO5A was observed in ESCC. We found that miR-190a-5p could directly bind with the mRNA of LINC01980 and MYO5A, and it was detected low expression in ESCC. We further demonstrated that the downregulation of MYO5A caused by overexpressing miR-190a-5p was released via upregulation of LINC01980. Functionally, LINC01980 acted as a competitively endogenous RNA (ceRNA) to impact the expression of MYO5A by sponging miR-190a-5p in ESCC. Therefore, these findings suggest that LINC01980 may act as an oncogenic lncRNA in ESCC and LINC01980/miR-190a-5p/MYO5A pathway contributes to the development of ESCC.

MicroRNA-5110 regulates pigmentation by cotargeting melanophilin and WNT family member 1.

Mammalian pigmentation requires the production of melanin by melanocytes and its transfer to neighboring keratinocytes. These complex processes are regulated by several molecular pathways. Melanophilin ( MLPH) and WNT family member 1 ( WNT1), known to be involved in melanin transfer and melanin production, respectively, were predicted to be targets of microRNA-5110 using bioinformatics. In the current study, we investigated the effects of microRNA-5110 on pigmentation in alpaca ( Vicugna pacos) melanocytes. In situ hybridization identified high levels of microRNA-5110 in the cytoplasm of alpaca melanocytes. Luciferase activity assays confirmed that MLPH and WNT1 were targeted by microRNA-5110 in these cells. Overexpression and knockdown of microRNA-5110 in alpaca melanocytes downregulated and upregulated MLPH and WNT1 expression at the mRNA and protein levels, respectively. In addition, overexpression and knockdown of microRNA-5110 in alpaca melanocytes decreased and increased, respectively, the mRNA levels of the melanin transfer-related genes, rat sarcoma (RAS)-associated binding ( RAB27a) and myosin 5a ( MYO5a); the mRNA levels of microphthalmia-associated transcription factor ( MITF), tyrosinase ( TYR), and tyrosinase-related protein ( TYRP) 1; and the production of total alkali melanin and pheomelanin. In contrast, overexpression and knockdown of microRNA-5110 increased and decreased the mRNA levels of TYRP2, respectively. Overexpression of microRNA-5110 also increased eumelanin. These results indicate that microRNA-5110 regulates pigmentation in alpaca melanocytes by directly targeting MLPH and WNT1 to affect eumelanin production and transfer.-Yang, S., Liu, B., Ji, K., Fan, R., Dong, C. MicroRNA-5110 regulates pigmentation by cotargeting melanophilin and WNT family member 1.

The ciliary membrane-associated proteome reveals actin-binding proteins as key components of cilia.

Primary cilia are sensory, antennae-like organelles present on the surface of many cell types. They have been involved in a variety of diseases collectively termed ciliopathies. As cilia are essential regulators of cell signaling, the composition of the ciliary membrane needs to be strictly regulated. To understand regulatory processes at the ciliary membrane, we report the targeting of a genetically engineered enzyme specifically to the ciliary membrane to allow biotinylation and identification of the membrane-associated proteome. Bioinformatic analysis of the comprehensive dataset reveals high-stoichiometric presence of actin-binding proteins inside the cilium. Immunofluorescence stainings and complementary interaction proteomic analyses confirm these findings. Depolymerization of branched F-actin causes further enrichment of the actin-binding and actin-related proteins in cilia, including Myosin 5a (Myo5a). Interestingly, Myo5a knockout decreases ciliation while enhanced levels of Myo5a are observed in cilia upon induction of ciliary disassembly. In summary, we present a novel approach to investigate dynamics of the ciliary membrane proteome in mammalian cells and identify actin-binding proteins as mechanosensitive components of cilia that might have important functions in cilia membrane dynamics.

Myosin Va mediates BDNF-induced postendocytic recycling of full-length TrkB and its translocation into dendritic spines.

Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal survival, neurite outgrowth and synaptic plasticity by activating the receptor tropomyosin receptor kinase B (TrkB, also known as NTRK2). TrkB has been shown to undergo recycling after BDNF stimulation. We have previously reported that full-length TrkB (TrkB-FL) are recycled through a Rab11-dependent pathway upon BDNF stimuli, which is important for the translocation of TrkB-FL into dendritic spines and for the maintenance of prolonged BDNF downstream signaling during long-term potentiation (LTP). However, the identity of the motor protein that mediates the local transfer of recycled TrkB-FL back to the plasma membrane remains unclear. Here, we report that the F-actin-based motor protein myosin Va (Myo5a) mediates the postendocytic recycling of TrkB-FL. Blocking the interaction between Rab11 and Myo5a by use of a TAT-tagged peptide consisting of amino acids 55-66 of the Myo5a ExonE domain weakened the association between TrkB-FL and Myo5a and thus impaired TrkB-FL recycling and BDNF-induced TrkB-FL translocation into dendritic spines. Finally, inhibiting Myo5a-mediated TrkB-FL recycling led to a significant reduction in prolonged BDNF downstream signaling. Taken together, these results show that Myo5a mediates BDNF-dependent TrkB-FL recycling and contributes to BDNF-induced TrkB spine translocation and prolonged downstream signaling.

Structural basis of cargo recognitions for class V myosins.

Class V myosins (MyoV), the most studied unconventional myosins, recognize numerous cargos mainly via the motor's globular tail domain (GTD). Little is known regarding how MyoV-GTD recognizes such a diverse array of cargos specifically. Here, we solved the crystal structures of MyoVa-GTD in its apo-form and in complex with two distinct cargos, melanophilin and Rab interacting lysosomal protein-like 2. The apo-MyoVa-GTD structure indicates that most mutations found in patients with Griscelli syndrome, microvillus inclusion disease, or cancers or in "dilute" rodents likely impair the folding of GTD. The MyoVa-GTD/cargo complex structure reveals two distinct cargo-binding surfaces, one primarily via charge-charge interaction and the other mainly via hydrophobic interactions. Structural and biochemical analysis reveal the specific cargo-binding specificities of various isoforms of mammalian MyoV as well as very different cargo recognition mechanisms of MyoV between yeast and higher eukaryotes. The MyoVa-GTD structures resolved here provide a framework for future functional studies of vertebrate class V myosins.

Pleiotropic effects of coat colour-associated mutations in humans, mice and other mammals.

The characterisation of the pleiotropic effects of coat colour-associated mutations in mammals illustrates that sensory organs and nerves are particularly affected by disorders because of the shared origin of melanocytes and neurocytes in the neural crest; e.g. the eye-colour is a valuable indicator of disorders in pigment production and eye dysfunctions. Disorders related to coat colour-associated alleles also occur in the skin (melanoma), reproductive tract and immune system. Additionally, the coat colour phenotype of an individual influences its general behaviour and fitness. Mutations in the same genes often produce similar coat colours and pleiotropic effects in different species (e.g., KIT [reproductive disorders, lethality], EDNRB [megacolon] and LYST [CHS]). Whereas similar disorders and similar-looking coat colour phenotypes sometimes have a different genetic background (e.g., deafness [EDN3/EDNRB, MITF, PAX and SNAI2] and visual diseases [OCA2, RAB38, SLC24A5, SLC45A2, TRPM1 and TYR]). The human predilection for fancy phenotypes that ignore disorders and genetic defects is a major driving force for the increase of pleiotropic effects in domestic species and laboratory subjects since domestication has commenced approximately 18,000 years ago.

Rare variant of large pediatric glioneuronal tumor with novel MYO5A::NTRK3 fusion: illustrative case.

BACKGROUND: Glioneuronal tumors (GNTs) comprise a rare class of central nervous system (CNS) neoplasms with varying degrees of neuronal and glial differentiation that predominately affect children and young adults. Within the current 2021 World Health Organization (WHO) classification of CNS tumors, GNTs encompass 14 distinct tumor types. Recently, the use of whole-genome DNA methylation profiling has allowed more precise classification of this tumor group. OBSERVATIONS: A 3-year-old male presented with a 3-month history of increasing head circumference, regression of developmental milestones, and speech delay. Magnetic resonance imaging of the brain was notable for a large left hemispheric multiseptated mass with significant mass effect and midline shift that was treated with near-total resection. Histological and molecular assessment demonstrated a glioneuronal tumor harboring an MYO5A::NTRK3 fusion. By DNA methylation profiling, this tumor matched to a provisional methylation class known as "glioneuronal tumor kinase-fused" (GNT kinase-fused). The patient was later started on targeted therapy with larotrectinib. LESSONS: This is the first report of an MYO5A::NTRK3 fusion in a pediatric GNT. GNT kinase-fused is a provisional methylation class not currently included in the WHO classification of CNS tumors. This case highlights the impact of thorough molecular characterization of CNS tumors, especially with the increasing availability of novel gene targeting therapies.

Evidence for origin of lavender foal syndrome among Egyptian Arabian horses in Egypt.

BACKGROUND: Lavender foal syndrome (LFS) is a fatal hereditary condition that is inherited in an autosomal recessive pattern. This detrimental mutation is more common in Arabian foals of Egyptian origin than foals from other bloodlines. Heterozygous horses are carriers of the LFS trait and appear normal, while recessive homozygous foals died shortly after birth due to serious complications. In Egypt, in 2014, an Egyptian foal died after manifestations of neurological signs and abnormal coat colour as LFS signs. Therefore, it is important to identify LFS carriers in the population of Arabian horses in Egypt and to encourage improvement of the Arabian horse industry in Egypt by constructing a breeding system based on genetic background in order to avoid mating between carriers and reduce financial losses from deaths of affected foals. OBJECTIVES: To establish a PCR-based test for detecting the MYO5A gene mutation causing LFS in the registered Arabian horse population in Egypt prior to breeding. STUDY DESIGN: Cross sectional survey (n = 170) plus targeted sampling (n = 30). METHODS: A total of 200 samples were collected from an Arabian farm in Egypt and some of them were traced for LFS based on the farm records. The LFS genotypes were identified using the PCR-RFLP technique, fragment analysis followed by sequence analysis. RESULTS: The overall mutated allele and genotype frequencies (N/L) were 0.08 and 16%, respectively. CONCLUSION: The observed frequency of heterozygotes suggests foals affected with LFS will be produced among Arabian horses in Egypt. Therefore, screening of the entire population for this mutation should be undertaken in the breeding program.

Central nervous system ganglioneuroblastoma harboring MYO5A-NTRK3 fusion.

Central nervous system (CNS) ganglioneuroblastoma is a rare neuroectodermal neoplasm and little is known about its clinical and biological features. Herein, we report a pediatric case of CNS ganglioneuroblastoma harboring MYO5A-NTRK3 fusion. The patient, a 4-year-old boy, underwent a partial resection of a supratentorial tumor that was histopathologically diagnosed as a CNS ganglioneuroblastoma. Treatment with radiotherapy was started per the St Jude Medulloblastoma 03 (SJMB03) protocol; however, the tumor progressed rapidly and radiotherapy was temporally discontinued. Meanwhile, the patient underwent a second surgery, in which a gross total resection was successfully performed, following which he completed the remaining protocol-based therapy. Although an early focal recurrence was detected for which he received additional radiotherapy and oral temozolomide, the patient remained in complete remission for 14 months after the completion of the treatment. A central pathological review and molecular analysis were performed that revealed a MYO5A-NTRK3 fusion. Interestingly, the MYO5A-NTRK3 fusion has been recurrently detected in melanocytic tumors but not in other types of tumors. Therefore, it can be speculated that our case might partly share tumorigenesis mechanisms with MYO5A-NTRK3-positive melanocytic tumors. In addition, our case may enable an improved understanding of the pathogenesis and clinical features of CNS ganglioneuroblastomas.

MYO5A inhibition by miR-145 acts as a predictive marker of occult neck lymph node metastasis in human laryngeal squamous cell carcinoma.

INTRODUCTION: Each year, ~50,000 patients worldwide die of laryngeal squamous cell carcinoma (LSCC) because of its highly metastatic properties. However, its pathogenic mechanisms are still unclear, and in particular, the prediction of metastasis remains elusive. This study aimed to define the role of microRNA-145 (miR-145) in LSCC progression. We also aimed to elucidate the clinical significance of the miR-145/MYO5A pathway, especially the predictive function of MYO5A in neck lymph node metastasis. MATERIALS AND METHODS: MYO5A and miR-145 expression was analyzed in 132 patients with LSCC, and associations between their expression and clinicopathological features were evaluated. We validated the regulatory relationship between miR-145b and MYO5A by dual luciferase reporter assay. The role of the miR-145/MYO5A pathway in proliferation, metastasis, and apoptosis was examined in vitro. The predictive functions of MYO5A in neck lymph node metastasis and prognosis were defined according to patient follow-up. RESULTS: Our results showed downregulation of miR-145 in LSCC, which was negatively correlated with MYO5A suppression of LSCC progression and metastasis. MiR-145 directly regulated MYO5A expression in vitro and suppressed LSCC proliferation and invasion while promoting apoptosis by inhibiting MYO5A. CONCLUSION: Notably, overexpression of serum MYO5A in LSCC predicted cervical nodal occult metastasis and poor prognosis, providing an effective indicator for predicting neck lymph node metastasis and assessing LSCC prognosis.

Pleiotropic neuropathological and biochemical alterations associated with Myo5a mutation in a rat Model.

In this study, we analyze the neuropathological and biochemical alterations involved in the pathogenesis of a neurodegenerative/movement disorder during different developmental stages in juvenile rats with a mutant Myosin5a (Myo5a). In mutant rats, a spontaneous autosomal recessive mutation characterized by the absence of Myo5a protein expression in the brain is associated with a syndrome of locomotor dysfunction, altered coat color, and neuroendocrine abnormalities. Myo5a encodes a myosin motor protein required for transport and proper distribution of subcellular organelles in somatodendritic processes in neurons. Here we report marked hyperphosphorylation of alpha-synuclein and tau, as well as region-specific buildup of the autotoxic dopamine metabolite, 3,4-dihydroxyphenyl-acetaldehyde (DOPAL), related to decreased aldehyde dehydrogenases activity and neurodegeneration in mutant rats. Alpha-synuclein accumulation in mitochondria of dopaminergic neurons is associated with impaired enzymatic respiratory complex I and IV activity. The behavioral and biochemical lesions progress after 15 days postnatal, and by 30-40 days the animals must be euthanized because of neurological impairment. Based on the obtained results, we propose a pleiotropic pathogenesis that links the Myo5a gene mutation to deficient neuronal development and progressive neurodegeneration. This potential model of a neurodevelopmental disorder with neurodegeneration and motor deficits may provide further insight into molecular motors and their associated proteins responsible for altered neurogenesis and neuronal disease pathogenesis.

New insights into the melanophilin (MLPH) gene controlling coat color phenotypes in American mink.

The mutation causing the Silverblue color type (pp) is one of the most used recessive mutations within American mink (Neovison vison) fur farming, since it is involved in some of the popular color types such as Violet and Saphire which originate from a combination of recessive mutations. In the present study, the genomic and mRNA sequences of the melanophilin (MLPH) gene were studied in Violet, Silverblue and wild-type (wt) mink animals. Although breeding schemes and previous literature indicates that the Violet (aammpp) phenotype is a triple recessive color type involving the same locus as the Silverblue (pp) color type, our findings indicate different genotypes at the MLPH locus. Upon comparison at genomic level, we identified two deletions of the entire intron 7 and of the 5' end of intron 8 in the sequence of the Silverblue MLPH gene. When investigating the mRNA, the Silverblue animals completely lack exon 8, which encodes 65 residues, of which 47 define the Myosin Va (MYO5A) binding domain. This may cause the incorrect anchoring of the MLPH protein to MYO5A in Silverblue animals, resulting in an improper pigmentation as seen in diluted phenotypes. Additionally, in the MLPH mRNA of wt, Violet and Silverblue phenotypes, part of intron 8 is retained resulting in a truncated MLPH protein, which is 359 residues long in wt and Violet and 284 residues long in Silverblue. Subsequently, our findings point out that the missing actin-binding domain, in neither of the 3 analyzed phenotypes affects the transport of melanosomes or the consequent final pigmentation. Moreover, the loss of the major part of the MYO5A domain in the Silverblue MLPH protein seems to be the responsible for the dilute phenotype. Based on our genomic DNA data, genetic tests for selecting Silverblue and Violet carrier animals can be performed in American mink.