OBJECTIVE: To analyze the characteristics of lysosomal enzymes in mucolipidosis (ML) type II α/β and type III α/β for the choice of enzyme evaluating indicators. METHODS: Multiple lysosomal enzymes including α-iduronidase (IDUA), α -N-acetylglucosaminidase (NAGLU), β-galactosidase-1 (GLB1), β-glucuronidase (GUSB), α-galactosidase A (GLA), glucocerebrosidase (GBA) and arylsulphatase A (ASA) in plasma and leukocyte of two Chinese pedigrees with ML type II α/β and type III α/β and healthy controls were determined. Previous publications on ML type II α/β and type III α/β during the last five years were retrieved from PubMed, CNKI and WanFang databases by using "mucolipidosis" as key word. RESULTS: The activities of several lysosomal enzymes were increased in the plasma of both patients: ASA, IDUA (20-fold) > GUSB (10-fold) > GLB1, GLA (5-fold) > NAGLU (2-fold), whilst there was no significant change in GBA. The activities of several lysosomal enzymes in the leukocyte of the two patients were normal. 15 lysosomal enzymes have been used in 22 previous studies, the most frequently used were hexosaminidase A and B (Hex A+B) (12 papers), α-mannosidase (α-man) (11 papers) and GUSB (10 papers). The degree of Hex A+B and α-man elevation was most obvious (24.4-fold and 24.7-fold on average respectively), followed by ASA (22.4-fold on average), GUSB is 18.8-fold on average. CONCLUSION Based on the lysosomal enzyme analysis of the two cases and literature review, ASA, GUSB, Hex A+B and α-man are recommended as the evaluating indicators for lysosomal enzyme analysis of ML type II α/β and type III α/β.
China ; Hexosaminidase A ; Humans ; Iduronidase ; Lysosomes ; Mucolipidoses/genetics* ; Pedigree

OBJECTIVE: To analyze the clinical features and genetic mutations in a patient with mucolipidosis type II α/β by using next generation sequencing. METHODS: Clinical data of the patient was collected. Genomic DNA of the patient and her parents was extracted by a standard method. The patient was subjected to targeted sequencing using an Ion Ampliseq panel, which included genes related to mucolipidosis and mucopolysaccharidosis. Suspected mutations were verified by Sanger sequencing. RESULTS: Compound heterozygous mutations, namely c.1284+1G>T and c.1090C>T (p.Arg364*), were detected in the patient, which were respectively inherited from her mother and father. No other disease-causing mutation was detected in the patient. GNPTAB c.1090C>T was known to be pathogenic, while GNPTAB c.1284+1G>T is a novel mutation. The same mutations were not detected among 50 healthy controls. CONCLUSION The compound heterozygous mutations c.1284+1G>T and c.1090C>T (p.Arg364*) of GNPTAB gene probably account for the mucolipidosis type II α/β in the patient. NGS has a great value for the molecular diagnosis and typing of mucolipidosis.
Female ; High-Throughput Nucleotide Sequencing ; Humans ; Mucolipidoses ; genetics ; Mutation ; Transferases (Other Substituted Phosphate Groups) ; genetics

OBJECTIVETo explore the clinical features and mutations of MYO5B gene in a family affected with microvillus inclusion disease.

METHODSClinical data of an infant affected with microvillus inclusion disease was collected. Genomic DNA was extracted from peripheral blood samples from the patient and her parents. PCR amplification and Sanger sequencing were performed to analyze all the exons and their flanking sequences of the MYO5B gene.

RESULTSThe patient presented with complicated manifestations including respiratory distress syndrome, dehydration, acidosis, bowel dilatation, liver and kidney dysfunction, and severe and intractable diarrhea. A compound mutation of the MYO5B gene, i.e., IVS37-1G>C/c.2729_2731delC (p.R911Afs916X), was discovered in the patient. The former was a splice-site mutation inherited from the mother, while the latter was a frameshift mutation inherited from the father. Both were not reported previously.

CONCLUSIONBased on the clinical and molecular evidence, the patient was diagnosed with microvillus inclusion disease. Above finding has expanded the mutation spectrum of the MYO5B gene, which can provide valuable information for genetic counseling for the family.

Family ; Female ; Genetic Testing ; methods ; Genotype ; Humans ; Infant ; Malabsorption Syndromes ; genetics ; Male ; Microvilli ; genetics ; pathology ; Mucolipidoses ; genetics ; Mutation ; genetics ; Myosin Heavy Chains ; genetics ; Myosin Type V ; genetics ; Phenotype

Microvillus inclusion disease (MVID) is an autosomal recessive disorder caused by biallelic mutations in the MYO5B or STX3 gene. Refractory diarrhea and malabsorption are the main clinical manifestations. The aim of this study was to investigate the clinical features and MYO5B gene mutations of an infant with MVID. A 21-day-old female infant was referred to the hospital with the complaint of diarrhea for 20 days. On physical examination, growth retardation of the body weight and length was found along with moderately jaundiced skin and sclera. Breath sounds were clear in the two lungs and the heart sounds were normal. The abdomen was distended and the veins in the abdominal wall were observed. The liver and spleen were not palpable. Biochemical analysis revealed raised serum total bile acids, bilirubin, transaminases and γ-glutamyl transpeptidase while decreased levels of serum sodium, chloride, phosphate and magnesium. Blood gas analysis indicated metabolic acidosis. The preliminary diagnosis was congenital diarrhea, and thus parenteral nutrition was given along with other symptomatic and supportive measures. However, diarrhea, metabolic acidosis and electrolyte disturbance were intractable, and the cholestatic indices, including transaminases, γ-glutamyl transpeptidase, bilirubin and total bile acids, remained at increased levels. One month later, the patient was discharged and then lost contact. On genetic analysis, the infant was proved to be a compound heterozygote of the c.310+2Tdup and c.1966C>T(p.R656C) variants of the gene MYO5B, with c.310+2Tdup being a novel splice-site mutation. MVID was thus definitely diagnosed.
Female ; Humans ; Infant, Newborn ; Malabsorption Syndromes ; diagnosis ; genetics ; Microvilli ; genetics ; pathology ; Mucolipidoses ; diagnosis ; genetics ; Mutation ; Myosin Heavy Chains ; genetics ; Myosin Type V ; genetics

OBJECTIVETo observe the alterations of the auditory function and morphology of the ear in the mouse sialidosis models which has been generated by targeted deletion of lysosomal neuraminidase gene (Neul) and closely resembled the phenotypes in corresponding human conditions, and to explore pathophysiological mechanisms of hearing impairment.

METHODSNeul homozygous (Neul -/-) mice at 3 weeks, 2 and 4 months of age, and their wildtype littermates (Neu1 +/+) were examined for auditory thresholds through auditory brainstem responses (ABR) to click, 8, 16, and 32 kHz stimuli. Morphological analyses in ears were performed by series temporal bone section and light microscopy.

RESULTSNeul -/- mice at 3 weeks of age showed an elevated ABR threshold, 50-55 dB above those of Neul +/+ mice. Up to 2 and 4 months of age, their thresholds were further elevated for 60-68 dB. There were distinct pathological changes of middle and inner ear of 3 weeks of age in Neul -/- mice, especially at 2-4 months of age there were significant cerumen occlusion in the external auditory canal and severe otitis media. Vacuolation associated with lysosomal storage was observed within ossicles and cochlear bone cells, stria vascularis cells, spiral ganglion neurons and macrophages, spiral limbus, spiral prominence, Reissner's membrane cells, and the mesothelial cells of the perilymphatic scala and basilar membrane, but not within the organ of Corti. Vestibular ganglion neurons, hair cells and supporting cells in cristae and maculae also showed vacuolation.

CONCLUSIONSThe deficiency of lysosomal neuraminidase may result in a serious hearing loss and morphological alterations of ear. The external auditory canal obstruction, otitis media and ossicle changes may cause conductive hearing loss, and the defects in lysosomal storage of neurons, stria vascularis, spiral limbus, Reissner's membrane and basilar membrane cells may contribute to sensorineural deafness.

Animals ; Ear, Middle ; anatomy & histology ; pathology ; Evoked Potentials, Auditory, Brain Stem ; Hearing Loss ; pathology ; physiopathology ; Mice ; Mice, Knockout ; Mucolipidoses ; pathology ; physiopathology ; Neuraminidase ; genetics ; Otitis Media ; pathology

TRPML1 channel is a non-selective group-2 transient receptor potential (TRP) channel with Ca permeability. Located mainly in late endosome and lysosome of all mammalian cell types, TRPML1 is indispensable in the processes of endocytosis, membrane trafficking, and lysosome biogenesis. Mutations of TRPML1 cause a severe lysosomal storage disorder called mucolipidosis type IV (MLIV). In the present study, we determined the cryo-electron microscopy (cryo-EM) structures of Mus musculus TRPML1 (mTRPML1) in lipid nanodiscs and Amphipols. Two distinct states of mTRPML1 in Amphipols are added to the closed state, on which could represent two different confirmations upon activation and regulation. The polycystin-mucolipin domain (PMD) may sense the luminal/extracellular stimuli and undergo a "move upward" motion during endocytosis, thus triggering the overall conformational change in TRPML1. Based on the structural comparisons, we propose TRPML1 is regulated by pH, Ca, and phosphoinositides in a combined manner so as to accommodate the dynamic endocytosis process.
Animals ; Calcium ; metabolism ; Cryoelectron Microscopy ; Endocytosis ; Endosomes ; metabolism ; Gene Expression ; HEK293 Cells ; Humans ; Hydrogen-Ion Concentration ; Lysosomes ; metabolism ; Mice ; Models, Biological ; Mucolipidoses ; genetics ; metabolism ; pathology ; Nanostructures ; chemistry ; ultrastructure ; Phosphatidylinositols ; metabolism ; Transgenes ; Transient Receptor Potential Channels ; chemistry ; genetics ; metabolism