ContextLysosomal storage disorders represent a group of at
least 41 genetically distinct, biochemically related, inherited
diseases. Individually, these disorders are considered rare, although
high prevalence values have been reported in some populations. These
disorders are devastating for individuals and their families and result
in considerable use of resources from health care systems; however, the
magnitude of the problem is not well defined. To date, no comprehensive
study has been performed on the prevalence of these disorders as a
group.ObjectiveTo determine the prevalence of lysosomal storage
disorders individually and as a group in the Australian population.DesignRetrospective case studies.SettingAustralia, from January 1, 1980, through December 31,
1996.Main Outcome MeasureEnzymatic diagnosis of a lysosomal storage
disorder.ResultsTwenty-seven different lysosomal storage disorders were
diagnosed in 545 individuals. The prevalence ranged from 1 per
57,000 live births for Gaucher disease to 1 per 4.2 million live
births for sialidosis. Eighteen of 27 disorders had more than 10
diagnosed cases. As a group of disorders, the combined prevalence was 1
per 7700 live births. There was no significant increase in the rate of
either clinical diagnoses or prenatal diagnoses of lysosomal storage
disorders during the study period.ConclusionsIndividually, lysosomal storage disorders are rare
genetic diseases. However, as a group, they are relatively common and
represent an important health problem in Australia.

https://jamanetwork.com/journals/jama/articlepdf/188380/JOC80368.pdf

Prevalence of lysosomal storage disorders.

Niemann-Pick type C2 disease (NP-C2) is a fatal hereditary disorder of unknown etiology characterized by defective egress of cholesterol from lysosomes. Here we show that the disease is caused by a deficiency in HE1, a ubiquitously expressed lysosomal protein identified previously as a cholesterol-binding protein. HE1 was undetectable in fibroblasts from NP-C2 patients but present in fibroblasts from unaffected controls and NP-C1 patients. Mutations in the HE1 gene, which maps to chromosome 14q24.3, were found in NP-C2 patients but not in controls. Treatment of NP-C2 fibroblasts with exogenous recombinant HE1 protein ameliorated lysosomal accumulation of low density lipoprotein-derived cholesterol.

https://science.sciencemag.org/content/sci/290/5500/2298.full.pdf

Identification of HE1 as the Second Gene of Niemann-Pick C Disease

Sorting of lysosomal proteins.

https://www.zora.uzh.ch/id/eprint/33361/3/Berger_et_al_The_molecular_basis_of_human_retinal_and_vitreoretinal_diseases_2010.pdf

The molecular basis of human retinal and vitreoretinal diseases.

Finland, located at the edge of the inhabitable world, is one of the best-studied genetic isolates. The characteristic features of population isolates-founder effect, genetic drift and isolation-have, over the centuries, shaped the gene pool of the Finns. Finnish diseases have been a target of extensive genetic research and the majority of some 35 disease genes enriched in this population have been identified; the molecular and cellular consequences of disease mutations are currently being characterized. Special strategies taking advantage of linkage disequilibrium have been efficiently used in the initial mapping and restriction of Finnish disease loci and this has stimulated development of novel statistical approaches in the disease gene hunt. Identification of mutated genes has provided tools for detailed analyses of molecular pathogenesis in Finnish diseases, many of which reveal a distinct tissue specificity of clinical phenotype. Often these studies have not only clarified the molecular detail of Finnish diseases, but also provided novel information on biological processes and metabolic pathways essential for normal development and function of human cells and tissues.

Molecular genetics of the Finnish disease heritage.

Classical late-infantile neuronal ceroid lipofuscinosis (LINCL) is a fatal neurodegenerative disease whose defective gene has remained elusive. A molecular basis for LINCL was determined with an approach applicable to other lysosomal storage diseases. When the mannose 6-phosphate modification of newly synthesized lysosomal enzymes was used as an affinity marker, a single protein was identified that is absent in LINCL. Sequence comparisons suggest that this protein is a pepstatin-insensitive lysosomal peptidase, and a corresponding enzymatic activity was deficient in LINCL autopsy specimens. Mutations in the gene encoding this protein were identified in LINCL patients but not in normal controls.

https://science.sciencemag.org/content/sci/277/5333/1802.full.pdf

Association of Mutations in a Lysosomal Protein with Classical Late-Infantile Neuronal Ceroid Lipofuscinosis

Two proteins have been implicated in the mannose 6-phosphate-dependent transport of lysosomal enzymes to lysosomes: the 300kDa cation-independent and the 46kDa cation-dependent mannose 6-phosphate receptors (CI- and CD-MPRs). The mammalian CI-MPR also mediates endocytosis and clearance of insulin-like growth factor II (IGF-II). Mutant mice that lack the CD-MPR are viable, mice that lack the CI-MPR accumulate high levels of IGF-II and usually die perinatally, whereas mice that lack both IGF-II and CI-MPR are viable. To investigate the relative roles of the MPRs in the targeting of lysosomal enzymes in vivo, we analysed the effect of a deficiency of either MPR on lysosomal enzyme activities in animals lacking IGF-II. In CD-MPR-deficient mice, most activities were relatively normal in solid tissues and some were marginally elevated in serum. In CI-MPR-deficient mice, some enzyme activities were moderately decreased in solid tissues and multiple enzymes were markedly elevated in serum. Finally, total levels of serum mannose 6-phosphorylated glycoproteins were approximately 45-fold and approximately 15-fold higher than wild type in CI- and CD-MPR-deficient mice respectively, and there were specific differences in the pattern of these proteins when comparing CI- and CD-MPR deficient animals. These results indicate that while lack of the CI-MPR appears to perturb lysosome function to a greater degree than lack of the CD-MPR, each MPR has distinct functions for the targeting of lysosomal enzymes in vivo.

/pdf/mouse-mutants-lacking-the-cation-independent-mannose-6-nnr5vdwslp.pdf

Mouse mutants lacking the cation-independent mannose 6-phosphate/insulin-like growth factor II receptor are impaired in lysosomal enzyme transport: Comparison of cation-independent and cation-dependent mannose 6-phosphate receptor-deficient mice

Structural organization and sequence of CLN2, the defective gene in classical late infantile neuronal ceroid lipofuscinosis

Lysosomes are membrane-bound, acidic eukaryotic cellular organelles that play important roles in the degradation of macromolecules. Mutations that cause the loss of lysosomal protein function can lead to a group of disorders categorized as the lysosomal storage diseases (LSDs). Suspicion of LSD is frequently based on clinical and pathologic findings, but in some cases, the underlying genetic and biochemical defects remain unknown. Here, we performed whole-exome sequencing (WES) on 14 suspected LSD cases to evaluate the feasibility of using WES for identifying causal mutations. By examining 2,157 candidate genes potentially associated with lysosomal function, we identified eight variants in five genes as candidate disease-causing variants in four individuals. These included both known and novel mutations. Variants were corroborated by targeted sequencing and, when possible, functional assays. In addition, we identified nonsense mutations in two individuals in genes that are not known to have lysosomal function. However, mutations in these genes could have resulted in phenotypes that were diagnosed as LSDs. This study demonstrates that WES can be used to identify causal mutations in suspected LSD cases. We also demonstrate cases where a confounding clinical phenotype may potentially reflect more than one lysosomal protein defect.

Chang Gong Liu

Papers

Association of Mutations in a Lysosomal Protein with Classical Late-Infantile Neuronal Ceroid Lipofuscinosis

Mouse mutants lacking the cation-independent mannose 6-phosphate/insulin-like growth factor II receptor are impaired in lysosomal enzyme transport: Comparison of cation-independent and cation-dependent mannose 6-phosphate receptor-deficient mice

Structural organization and sequence of CLN2, the defective gene in classical late infantile neuronal ceroid lipofuscinosis

Using whole-exome sequencing to investigate the genetic bases of lysosomal storage diseases of unknown etiology.