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Genetics and Molecular Biology 2023Mucolipidosis II and III (MLII and MLIII) are autosomal recessive diseases caused by pathogenic variants in GNPTAB and GNPTG genes that lead to defects in...
Mucolipidosis II and III (MLII and MLIII) are autosomal recessive diseases caused by pathogenic variants in GNPTAB and GNPTG genes that lead to defects in GlcNAc-1-phosphotransferase. This enzyme adds mannose 6-phosphate residues to lysosomal hydrolases, which allows enzymes to enter lysosomes. Defective GlcNAc-1-phosphotransferase causes substrate accumulation and inflammation. These diseases have no treatment, and we hypothesized that the use of substrate reduction therapy and immunomodulation may be beneficial at the cell level and as a future therapeutic approach. Fibroblasts from two patients with MLIII alpha/beta and 2 patients with MLIII gamma as well as from one healthy control were treated with 10 µM miglustat, 20 µM genistein, and 20 µM thalidomide independently. ELISA assay and confocal immunofluorescence microscopy were used to evaluate the presence of heparan sulfate (HS) and the impact on substrate accumulation. ELISA assay showed HS reduction in all patients with the different treatments used (p=0.05). HS reduction was also observed by immunofluorescence microscopy. Our study produced encouraging results, since the reduction in substrate accumulation, even partial, may offer benefits to the phenotype of patients with inborn errors of metabolism.
PubMed: 38047750
DOI: 10.1590/1678-4685-GMB-2023-0117 -
Data in Brief Dec 2023Retinal degenerative diseases (RDDs) are a diverse group of retinal disorders that cause visual impairment. While RDD prevalence is high, little is known about the...
Retinal degenerative diseases (RDDs) are a diverse group of retinal disorders that cause visual impairment. While RDD prevalence is high, little is known about the molecular mechanisms underlying the pathogenesis within many of these disorders. Here we use transcriptome analysis to elucidate the molecular mechanisms that drive early onset photoreceptor neuron function loss in the mouse model of the RDD Mucolipidosis type IV (MLIV). MLIV is a lysosomal storage disorder resulting from loss of function mutations in the gene. encodes a lysosomal cation channel, the transient receptor potential channel mucolipin 1 (Trpml1). To identify changes in gene expression during onset in MLIV we used a genetic mouse model () which recapitulates clinical attributes of the human disease. We conducted transcriptome analysis in 6-week old control and mice under normal 12:12 light cycle as well as low and high light stress conditions. These data will be valuable to the vision research community for identifying differentially expressed in early onset MLIV potentially leading to new insights into the pathophysiology of this RDD. Raw FASTQ files and processed counts files for the RNA-seq libraries are deposited in the NCBI Sequence Read Archive (SRA) and have been assigned BioProject accession PRJNA1002601 [1].
PubMed: 38020430
DOI: 10.1016/j.dib.2023.109659 -
Cells Nov 2023The recently presented Azalea Hypothesis for Alzheimer's disease asserts that iron becomes sequestered, leading to a functional iron deficiency that contributes to... (Review)
Review
The recently presented Azalea Hypothesis for Alzheimer's disease asserts that iron becomes sequestered, leading to a functional iron deficiency that contributes to neurodegeneration. Iron sequestration can occur by iron being bound to protein aggregates, such as amyloid β and tau, iron-rich structures not undergoing recycling (e.g., due to disrupted ferritinophagy and impaired mitophagy), and diminished delivery of iron from the lysosome to the cytosol. Reduced iron availability for biochemical reactions causes cells to respond to acquire additional iron, resulting in an elevation in the total iron level within affected brain regions. As the amount of unavailable iron increases, the level of available iron decreases until eventually it is unable to meet cellular demands, which leads to a functional iron deficiency. Normally, the lysosome plays an integral role in cellular iron homeostasis by facilitating both the delivery of iron to the cytosol (e.g., after endocytosis of the iron-transferrin-transferrin receptor complex) and the cellular recycling of iron. During a lysosomal storage disorder, an enzyme deficiency causes undigested substrates to accumulate, causing a sequelae of pathogenic events that may include cellular iron dyshomeostasis. Thus, a functional deficiency of iron may be a pathogenic mechanism occurring within several lysosomal storage diseases and Alzheimer's disease.
Topics: Humans; Alzheimer Disease; Iron; Amyloid beta-Peptides; Lysosomal Storage Diseases; Lysosomes; Iron Deficiencies
PubMed: 37998376
DOI: 10.3390/cells12222641 -
American Journal of Ophthalmology Feb 2024To report the genetic etiology of Lisch epithelial corneal dystrophy (LECD).
PURPOSE
To report the genetic etiology of Lisch epithelial corneal dystrophy (LECD).
DESIGN
Multicenter cohort study.
METHODS
A discovery cohort of 27 individuals with LECD from 17 families, including 7 affected members from the original LECD family, 6 patients from 2 new families and 14 simplex cases, was recruited. A cohort of 6 individuals carrying a pathogenic MCOLN1 (mucolipin 1) variant was reviewed for signs of LECD. Next-generation sequencing or targeted Sanger sequencing were used in all patients to identify pathogenic or likely pathogenic variants and penetrance of variants.
RESULTS
Nine rare heterozygous MCOLN1 variants were identified in 23 of 27 affected individuals from 13 families. The truncating nature of 7 variants and functional testing of 1 missense variant indicated that they result in MCOLN1 haploinsufficiency. Importantly, in the homozygous and compound-heterozygous state, 4 of 9 LECD-associated variants cause the rare lysosomal storage disorder mucolipidosis IV (MLIV). Autosomal recessive MLIV is a systemic disease and comprises neurodegeneration as well as corneal opacity of infantile-onset with epithelial autofluorescent lysosomal inclusions. However, the 6 parents of 3 patients with MLIV confirmed to carry pathogenic MCOLN1 variants did not have the LECD phenotype, suggesting MCOLN1 haploinsufficiency may be associated with reduced penetrance and variable expressivity.
CONCLUSIONS
MCOLN1 haploinsufficiency is the major cause of LECD. Based on the overlapping clinical features of corneal epithelial cells with autofluorescent inclusions reported in both LECD and MLIV, it is concluded that some carriers of MCOLN1 haploinsufficiency-causing variants present with LECD.
Topics: Humans; Transient Receptor Potential Channels; Cohort Studies; Mucolipidoses; Corneal Dystrophies, Hereditary
PubMed: 37972748
DOI: 10.1016/j.ajo.2023.10.011 -
Diabetologia Jan 2024Monogenic diabetes is estimated to account for 1-6% of paediatric diabetes cases in primarily non-consanguineous populations, while the incidence and genetic spectrum in...
AIMS/HYPOTHESIS
Monogenic diabetes is estimated to account for 1-6% of paediatric diabetes cases in primarily non-consanguineous populations, while the incidence and genetic spectrum in consanguineous regions are insufficiently defined. In this single-centre study we aimed to evaluate diabetes subtypes, obtain the consanguinity rate and study the genetic background of individuals with syndromic and neonatal diabetes in a population with a high rate of consanguinity.
METHODS
Data collection was carried out cross-sectionally in November 2021 at the paediatric diabetic clinic, Dr Jamal Ahmad Rashed Hospital, in Sulaimani, Kurdistan, Iraq. At the time of data collection, 754 individuals with diabetes (381 boys) aged up to 16 years were registered. Relevant participant data was obtained from patient files. Consanguinity status was known in 735 (97.5%) participants. Furthermore, 12 families of children with neonatal diabetes and seven families of children with syndromic diabetes consented to genetic testing by next-generation sequencing. Prioritised variants were evaluated using the American College of Medical Genetics and Genomics guidelines and confirmed by Sanger sequencing.
RESULTS
A total of 269 of 735 participants (36.5%) with known consanguinity status were offspring of consanguineous families. An overwhelming majority of participants (714/754, 94.7%) had clinically defined type 1 diabetes (35% of them were born to consanguineous parents), whereas only eight (1.1%) had type 2 diabetes (38% consanguineous). Fourteen (1.9%) had neonatal diabetes (50% consanguineous), seven (0.9%) had syndromic diabetes (100% consanguineous) and 11 (1.5%) had clinically defined MODY (18% consanguineous). We found that consanguinity was significantly associated with syndromic diabetes (p=0.0023) but not with any other diabetes subtype. The genetic cause was elucidated in ten of 12 participants with neonatal diabetes who consented to genetic testing (homozygous variants in GLIS3 [sibling pair], PTF1A and ZNF808 and heterozygous variants in ABCC8 and INS) and four of seven participants with syndromic diabetes (homozygous variants in INSR, SLC29A3 and WFS1 [sibling pair]). In addition, a participant referred as syndromic diabetes was diagnosed with mucolipidosis gamma and probably has type 2 diabetes.
CONCLUSIONS/INTERPRETATION
This unique single-centre study confirms that, even in a highly consanguineous population, clinically defined type 1 diabetes is the prevailing paediatric diabetes subtype. Furthermore, a pathogenic cause of monogenic diabetes was identified in 83% of tested participants with neonatal diabetes and 57% of participants with syndromic diabetes, with most variants being homozygous. Causative genes in our consanguineous participants were markedly different from genes reported from non-consanguineous populations and also from those reported in other consanguineous populations. To correctly diagnose syndromic diabetes in consanguineous populations, it may be necessary to re-evaluate diagnostic criteria and include additional phenotypic features such as short stature and hepatosplenomegaly.
Topics: Male; Infant, Newborn; Humans; Child; Aged; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Consanguinity; Cohort Studies; Iraq; Infant, Newborn, Diseases; Mutation; Nucleoside Transport Proteins
PubMed: 37897565
DOI: 10.1007/s00125-023-06030-2 -
BMC Ophthalmology Sep 2023We describe the case of a 47-year-old man referred to a retinal clinic and diagnosed with late-onset retinitis pigmentosa. Surprisingly, genetic testing revealed...
BACKGROUND
We describe the case of a 47-year-old man referred to a retinal clinic and diagnosed with late-onset retinitis pigmentosa. Surprisingly, genetic testing revealed compound heterozygous pathogenic variants in GNPTG, leading to the diagnosis of the autosomal recessive lysosomal storage disorder mucolipidosis type III gamma. Mucolipidosis type III gamma is typically diagnosed during childhood due to symptoms relating to skeletal dysplasia. Retinal dystrophy is not a common phenotypic feature.
CASE PRESENTATION
Ophthalmologic examination was consistent with a mild form of retinitis pigmentosa and included fundus photography, measurement of best-corrected visual acuity, optical coherence tomography, electroretinogram and visual field testing. Extraocular findings included joint restriction and pains from an early age leading to bilateral hip replacement by age 30, aortic insufficiency, and hypertension. Genetic analysis was performed by whole genome sequencing filtered for a gene panel of 325 genes associated with retinal disease. Two compound heterozygous pathogenic variants were identified in GNPTG, c.347_349del and c.607dup. The diagnosis of mucolipidosis type III gamma was confirmed biochemically by measurement of increased activities of specific lysosomal enzymes in plasma.
CONCLUSION
To our knowledge this is the first description of retinitis pigmentosa caused by compound heterozygous variants in GNPTG, providing further indications that late-onset retinal dystrophy is part of the phenotypic spectrum of mucolipidosis type III gamma.
Topics: Male; Humans; Adult; Middle Aged; Mucolipidoses; Whole Genome Sequencing; Electroretinography; Retinal Dystrophies; Transferases (Other Substituted Phosphate Groups)
PubMed: 37752499
DOI: 10.1186/s12886-023-03136-4 -
JCI Insight Oct 2023Sialidosis is an ultra-rare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe type II form of the disease manifests with...
Sialidosis is an ultra-rare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe type II form of the disease manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology, and visceromegaly. A subset of these patients present with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in 2 NEU1-deficient mouse models, a constitutive Neu1-knockout, Neu1ΔEx3, and a conditional phagocyte-specific knockout, Neu1Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles, and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal distal tubules, and distal tubules was drastically increased, including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalin-mediated protein reabsorption.
Topics: Animals; Humans; Mice; Kidney Diseases; Kidney Glomerulus; Kidney Tubules, Proximal; Low Density Lipoprotein Receptor-Related Protein-2; Mucolipidoses; Neuraminidase
PubMed: 37698928
DOI: 10.1172/jci.insight.166470 -
The Journal of Clinical Investigation Oct 2023Microvillus inclusion disease (MVID), caused by loss-of-function mutations in the motor protein myosin Vb (MYO5B), is a severe infantile disease characterized by...
Microvillus inclusion disease (MVID), caused by loss-of-function mutations in the motor protein myosin Vb (MYO5B), is a severe infantile disease characterized by diarrhea, malabsorption, and acid/base instability, requiring intensive parenteral support for nutritional and fluid management. Human patient-derived enteroids represent a model for investigation of monogenic epithelial disorders but are a rare resource from MVID patients. We developed human enteroids with different loss-of function MYO5B variants and showed that they recapitulated the structural changes found in native MVID enterocytes. Multiplex immunofluorescence imaging of patient duodenal tissues revealed patient-specific changes in localization of brush border transporters. Functional analysis of electrolyte transport revealed profound loss of Na+/H+ exchange (NHE) activity in MVID patient enteroids with near-normal chloride secretion. The chloride channel-blocking antidiarrheal drug crofelemer dose-dependently inhibited agonist-mediated fluid secretion. MVID enteroids exhibited altered differentiation and maturation versus healthy enteroids. γ-Secretase inhibition with DAPT recovered apical brush border structure and functional Na+/H+ exchange activity in MVID enteroids. Transcriptomic analysis revealed potential pathways involved in the rescue of MVID cells including serum/glucocorticoid-regulated kinase 2 (SGK2) and NHE regulatory factor 3 (NHERF3). These results demonstrate the utility of patient-derived enteroids for developing therapeutic approaches to MVID.
Topics: Humans; Microvilli; Myosin Heavy Chains; Myosin Type V; Enterocytes; Malabsorption Syndromes; Mucolipidoses
PubMed: 37643022
DOI: 10.1172/JCI169234 -
Frontiers in Molecular Neuroscience 2023Mucolipidosis IV (MLIV) is an ultra-rare, recessively inherited lysosomal disorder resulting from inactivating mutations in , the gene encoding the lysosomal cation...
Mucolipidosis IV (MLIV) is an ultra-rare, recessively inherited lysosomal disorder resulting from inactivating mutations in , the gene encoding the lysosomal cation channel TRPML1. The disease primarily affects the central nervous system (CNS) and manifests in the first year with cognitive and motor developmental delay, followed by a gradual decline in neurological function across the second decade of life, blindness, and premature death in third or fourth decades. Brain pathology manifestations in MLIV are consistent with hypomyelinating leukodystrophy with brain iron accumulation. Presently, there are no approved or investigational therapies for MLIV, and pathogenic mechanisms remain largely unknown. The MLIV mouse model, mice, recapitulates all major manifestations of the human disease. Here, to better understand the pathological mechanisms in the MLIV brain, we performed cell type specific LC-MS/MS proteomics analysis in the MLIV mouse model and reconstituted molecular signatures of the disease in either freshly isolated populations of neurons, astrocytes, oligodendrocytes, and neural stem cells, or whole tissue cortical homogenates from young adult symptomatic mice. Our analysis confirmed on the molecular level major histopathological hallmarks of MLIV universally present in tissue and brain cells, such as hypomyelination, lysosomal dysregulation, and impaired metabolism of lipids and polysaccharides. Importantly, pathway analysis in brain cells revealed mitochondria-related alterations in all brain cells, except oligodendrocytes, that was not possible to resolve in whole tissue. We also report unique proteome signatures and dysregulated pathways for each brain cell population used in this study. These data shed new light on cell-intrinsic mechanisms of MLIV and provide new insights for biomarker discovery and validation to advance translational studies for this disease.
PubMed: 37609073
DOI: 10.3389/fnmol.2023.1215425 -
Orphanet Journal of Rare Diseases Aug 2023Inborn metabolic diseases (IMD) are rare conditions that can be diagnosed during adulthood. Patients with IMD may have joint symptoms and the challenge is to establish... (Review)
Review
Inborn metabolic diseases (IMD) are rare conditions that can be diagnosed during adulthood. Patients with IMD may have joint symptoms and the challenge is to establish an early diagnosis in order to institute appropriate treatment and prevent irreversible damage. This review describes the joint manifestations of IMD that may be encountered in adults. The clinical settings considered were arthralgia and joint stiffness as well as arthritis. Unspecific arthralgias are often the first symptoms of hereditary hemochromatosis, chronic low back pain may reveal an intervertebral disc calcification in relation with alkaptonuria, and progressive joint stiffness may correspond to a mucopolysaccharidosis or mucolipidosis. Gaucher disease is initially revealed by painful acute attacks mimicking joint pain described as "bone crises". Some IMD may induce microcrystalline arthropathy. Beyond classical gout, there are also gouts in connection with purine metabolism disorders known as "enzymopathic gouts". Pyrophosphate arthropathy can also be part of the clinical spectrum of Gitelman syndrome or hypophosphatasia. Oxalate crystals arthritis can reveal a primary hyperoxaluria. Destructive arthritis may be indicative of Wilson's disease. Non-destructive arthritis may be seen in mevalonate kinase deficiency and familial hypercholesterolemia.
Topics: Humans; Adult; Chondrocalcinosis; Gout; Joint Diseases; Metabolism, Inborn Errors; Hepatolenticular Degeneration
PubMed: 37563694
DOI: 10.1186/s13023-023-02810-6