Mutation in the gene encoding lysosomal acid phosphatase (Acp2) causes cerebellum and skin malformation in mouse

A systems biology-based identification and in vivo functional screening of Alzheimer's disease risk genes reveal modulators of memory function

Genome-wide association studies (GWASs) have uncovered over 75 genomic loci associated with risk for late-onset Alzheimer's disease (LOAD), but identification of the underlying causal genes remains challenging. Studies of induced pluripotent stem cell (iPSC)-derived neurons from LOAD patients have demonstrated the existence of neuronal cell-intrinsic functional defects. Here, we searched for genetic contributions to neuronal dysfunction in LOAD using an integrative systems approach that incorporated multi-evidence-based gene mapping and network-analysis-based prioritization. A systematic perturbation screening of candidate risk genes in Caenorhabditis elegans (C. elegans) revealed that neuronal knockdown of the LOAD risk gene orthologs vha-10 (ATP6V1G2), cmd-1 (CALM3), amph-1 (BIN1), ephx-1 (NGEF), and pho-5 (ACP2) alters short-/intermediate-term memory function, the cognitive domain affected earliest during LOAD progression. These results highlight the impact of LOAD risk genes on evolutionarily conserved memory function, as mediated through neuronal endosomal dysfunction, and identify new targets for further mechanistic interrogation.

Comprehensive Analysis and Experimental Validation of the Parkinson's Disease Lysosomal Gene ACP2 and Pan-cancer

The pivotal role of lysosomal function in preserving neuronal homeostasis is recognized, with its dysfunction being implicated in neurodegenerative processes, notably in Parkinson's disease (PD). Yet, the molecular underpinnings of lysosome-related genes (LRGs) in the context of PD remain partially elucidated. We collected RNA-seq data from the brain substantia nigra of 30 PD patients and 20 normal subjects from the GEO database. We obtained molecular classification clusters from the screened lysosomal expression patterns. The lysosome-related diagnostic model of Parkinson's disease was constructed by XGBoost and Random Forest. And we validated the expression patterns of signature LRGs in the diagnostic model by constructing a PD rat model. Finally, the linkage between PD and cancer through signature genes was explored. The expression patterns of the 33 LRGs screened can be divided into two groups of PD samples, enabling exploration of the variance in biological processes and immune elements. Cluster A had a higher disease severity. Subsequently, critical genes were sieved through the application of machine learning methodologies culminating in the identification of two intersecting feature genes (ACP2 and LRP2). A PD risk prediction model was constructed grounded on these signature genes. The model's validity was assessed through nomogram evaluation, which demonstrated robust confidence validity. Then we analyzed the correlation analysis, immune in-filtration, biological function, and rat expression validation of the two genes with common pathogenic genes in Parkinson's disease, indicating that these two genes play an important role in the pathogenesis of PD. We then selected ACP2, which had a significant immune infiltration correlation, as the entry gene for the pan-cancer analysis. The pan-cancer analysis revealed that ACP2 has profound associations with prognostic indicators, immune infiltration, and tumor-related regulatory processes across various neoplasms, suggesting its potential as a therapeutic target in a range of human diseases, including PD and cancers. Our study comprehensively analyzed the molecular grouping of LRGs expression patterns in Parkinson's disease, and the disease progression was more severe in cluster A. And the PD diagnosis model related to LRGs is constructed. Finally, ACP2 is a potential target for the relationship between Parkinson's disease and tumor.

Endosomal dysfunction contributes to cerebellar deficits in spinocerebellar ataxia type 6

Spinocerebellar ataxia type 6 (SCA6) is a rare disease that is characterized by cerebellar dysfunction. Patients have progressive motor coordination impairment, and postmortem brain tissue reveals degeneration of cerebellar Purkinje cells and a reduced level of cerebellar brain-derived neurotrophic factor (BDNF). However, the pathophysiological changes underlying SCA6 are not fully understood. We carried out RNA-sequencing of cerebellar vermis tissue in a mouse model of SCA6, which revealed widespread dysregulation of genes associated with the endo-lysosomal system. Since disruption to endosomes or lysosomes could contribute to cellular deficits, we examined the endo-lysosomal system in SCA6. We identified alterations in multiple endosomal compartments in the Purkinje cells of SCA6 mice. Early endosomes were enlarged, while the size of the late endosome compartment was reduced. We also found evidence for impaired trafficking of cargo to the lysosomes. As the proper functioning of the endo-lysosomal system is crucial for the sorting and trafficking of signaling molecules, we wondered whether these changes could contribute to previously identified deficits in signaling by BDNF and its receptor tropomyosin kinase B (TrkB) in SCA6. Indeed, we found that the enlarged early endosomes in SCA6 mice accumulated both BDNF and TrkB. Furthermore, TrkB recycling to the cell membrane in recycling endosomes was reduced, and the late endosome transport of BDNF for degradation was impaired. Therefore, mis-trafficking due to aberrant endo-lysosomal transport and function could contribute to SCA6 pathophysiology through alterations to BDNF-TrkB signaling, as well as mishandling of other signaling molecules. Deficits in early endosomes and BDNF localization were rescued by chronic administration of a TrkB agonist, 7,8-dihydroxyflavone, that we have previously shown restores motor coordination and cerebellar TrkB expression. The endo-lysosomal system is thus both a novel locus of pathophysiology in SCA6 and a promising therapeutic target.

Genes in human obesity loci are causal obesity genes in C. elegans

Obesity and its associated metabolic syndrome are a leading cause of morbidity and mortality. Given the disease's heavy burden on patients and the healthcare system, there has been increased interest in identifying pharmacological targets for the treatment and prevention of obesity. Towards this end, genome-wide association studies (GWAS) have identified hundreds of human genetic variants associated with obesity. The next challenge is to experimentally define which of these variants are causally linked to obesity, and could therefore become targets for the treatment or prevention of obesity. Here we employ high-throughput in vivo RNAi screening to test for causality 293 C. elegans orthologs of human obesity-candidate genes reported in GWAS. We RNAi screened these 293 genes in C. elegans subject to two different feeding regimens: (1) regular diet, and (2) high-fructose diet, which we developed and present here as an invertebrate model of diet-induced obesity (DIO). We report 14 genes that promote obesity and 3 genes that prevent DIO when silenced in C. elegans. Further, we show that knock-down of the 3 DIO genes not only prevents excessive fat accumulation in primary and ectopic fat depots but also improves the health and extends the lifespan of C. elegans overconsuming fructose. Importantly, the direction of the association between expression variants in these loci and obesity in mice and humans matches the phenotypic outcome of the loss-of-function of the C. elegans ortholog genes, supporting the notion that some of these genes would be causally linked to obesity across phylogeny. Therefore, in addition to defining causality for several genes so far merely correlated with obesity, this study demonstrates the value of model systems compatible with in vivo high-throughput genetic screening to causally link GWAS gene candidates to human diseases.

Reduced Granule Cell Proliferation and Molecular Dysregulation in the Cerebellum of Lysosomal Acid Phosphatase 2 (ACP2) Mutant Mice

Lysosomal acid phosphatase 2 (Acp2) mutant mice (naked-ataxia, nax) have a severe cerebellar cortex defect with a striking reduction in the number of granule cells. Using a combination of in vivo and in vitro immunohistochemistry, Western blotting, BrdU assays, and RT-qPCR, we show downregulation of MYCN and dysregulation of the SHH signaling pathway in the nax cerebellum. MYCN protein expression is significantly reduced at P10, but not at the peak of proliferation at around P6 when the number of granule cells is strikingly reduced in the nax cerebellum. Despite the significant role of the SHH-MycN pathway in granule cell proliferation, our study suggests that a broader molecular pathway and additional mechanisms regulating granule cell development during the clonal expansion period are impaired in the nax cerebellum. In particular, our results indicate that downregulation of the protein synthesis machinery may contribute to the reduced number of granule cells in the nax cerebellum.

Clinical and molecular evaluation of 13 Brazilian patients with Gomez-López-Hernández syndrome

We aim to characterize patients with Gomez-López-Hernández syndrome (GLHS) clinically and to investigate them molecularly. A clinical protocol, including a morphological and neuropsychological assessment, was applied to 13 patients with GLHS. Single-nucleotide polymorphism (SNP) array and whole-exome sequencing were undertaken; magnetic resonance imaging was performed in 12 patients, including high-resolution, heavily T2-weighted sequences (HRT2) in 6 patients to analyze the trigeminal nerves. All patients presented alopecia; two did not present rhombencephalosynapsis (RES); trigeminal anesthesia was present in 5 of the 11 patients (45.4%); brachycephaly/brachyturricephaly and mid-face retrusion were found in 84.6 and 92.3% of the patients, respectively. One patient had intellectual disability. HRT2 sequences showed trigeminal nerve hypoplasia in four of the six patients; all four had clinical signs of trigeminal anesthesia. No common candidate gene was found to explain GLHS phenotype. RES does not seem to be an obligatory finding in respect of GLHS diagnosis. We propose that a diagnosis of GLHS should be considered in patients with at least two of the following criteria: focal non-scarring alopecia, rhombencephalosynapsis, craniofacial anomalies (brachyturrycephaly, brachycephaly or mid-face retrusion), trigeminal anesthesia or anatomic abnormalities of the trigeminal nerve. Studies focusing on germline whole genome sequencing or DNA and/or RNA sequencing of the alopecia tissue may be the next step for the better understanding of GLHS etiology.

Whole exome sequencing study identifies novel rare and common Alzheimer's-Associated variants involved in immune response and transcriptional regulation

The Alzheimer's Disease Sequencing Project (ADSP) undertook whole exome sequencing in 5,740 late-onset Alzheimer disease (AD) cases and 5,096 cognitively normal controls primarily of European ancestry (EA), among whom 218 cases and 177 controls were Caribbean Hispanic (CH). An age-, sex- and APOE based risk score and family history were used to select cases most likely to harbor novel AD risk variants and controls least likely to develop AD by age 85 years. We tested ~1.5 million single nucleotide variants (SNVs) and 50,000 insertion-deletion polymorphisms (indels) for association to AD, using multiple models considering individual variants as well as gene-based tests aggregating rare, predicted functional, and loss of function variants. Sixteen single variants and 19 genes that met criteria for significant or suggestive associations after multiple-testing correction were evaluated for replication in four independent samples; three with whole exome sequencing (2,778 cases, 7,262 controls) and one with genome-wide genotyping imputed to the Haplotype Reference Consortium panel (9,343 cases, 11,527 controls). The top findings in the discovery sample were also followed-up in the ADSP whole-genome sequenced family-based dataset (197 members of 42 EA families and 501 members of 157 CH families). We identified novel and predicted functional genetic variants in genes previously associated with AD. We also detected associations in three novel genes: IGHG3 (p = 9.8 × 10-7), an immunoglobulin gene whose antibodies interact with β-amyloid, a long non-coding RNA AC099552.4 (p = 1.2 × 10-7), and a zinc-finger protein ZNF655 (gene-based p = 5.0 × 10-6). The latter two suggest an important role for transcriptional regulation in AD pathogenesis.

Mutations in the Reelin pathway are associated with abnormal expression of microglial IgG FC receptors in the cerebellar cortex

Microglia are the immune cells of the central nervous system involved in a variety of developmental processes, such as regulation of cell death and survival, spatial patterning, and contribute to the development of Purkinje cells (PCs) during migration. Microglia express immunoglobulin G Fc receptors (FcgRs). In this report, we describe microglial FcgR expression and its relation to abnormal PC migration in the cerebellum during development. To detect microglial FcgR, the direct anti-IgG (secondary antisera) and high concentrations of Triton X-100 were applied as a method for labeling microglial cells without the use of any specific primary antiserum. By using Acp2^-/- mice, which show an excessive PC migration into the molecular layer (ml), and 3 different types of mice with a null to alter the Reelin pathway (Reeler-, Dab1 (SCM)-, and Apoer mutant mice), we studied the location of PCs and the expression of FcgRs. Wild type littermates were used as controls in all studies. We show that the expression of microglial FcgRs was absent and PCs were ectopically located in the white matter in the cerebella of all mutant mice, except for the Acp2^-/- mice (PCs were located in the ml). These results suggest a role for FcgRs in the Reelin signaling pathway, not in regulating PC migration, but rather in the adaptation to an environment with a relatively large number of ectopically located PCs. However, the exact correlation between the ectopic location of PCs and lack of FcgRs in Reeler, SCM, and Apoer^-/- mice and the presence of FcgRs and directed PC location in the ml in Acp2^-/- mice are yet to be determined.

Genome-Wide Association Study Reveals a Novel Association Between MYBPC3 Gene Polymorphism, Endurance Athlete Status, Aerobic Capacity and Steroid Metabolism

Background

The genetic predisposition to elite athletic performance has been a controversial subject due to the underpowered studies and the small effect size of identified genetic variants. The aims of this study were to investigate the association of common single-nucleotide polymorphisms (SNPs) with endurance athlete status in a large cohort of elite European athletes using GWAS approach, followed by replication studies in Russian and Japanese elite athletes and functional validation using metabolomics analysis.

Results

The association of 476,728 SNPs of Illumina DrugCore Gene chip and endurance athlete status was investigated in 796 European international-level athletes (645 males, 151 females) by comparing allelic frequencies between athletes specialized in sports with high (n = 662) and low/moderate (n = 134) aerobic component. Replication of results was performed by comparing the frequencies of the most significant SNPs between 242 and 168 elite Russian high and low/moderate aerobic athletes, respectively, and between 60 elite Japanese endurance athletes and 406 controls. A meta-analysis has identified rs1052373 (GG homozygotes) in Myosin Binding Protein (MYBPC3; implicated in cardiac hypertrophic myopathy) gene to be associated with endurance athlete status (P = 1.43 × 10^-8, odd ratio 2.2). Homozygotes carriers of rs1052373 G allele in Russian athletes had significantly greater VO_{2 max} than carriers of the AA + AG (P = 0.005). Subsequent metabolomics analysis revealed several amino acids and lipids associated with rs1052373 G allele (1.82 × 10^-05) including the testosterone precursor androstenediol (3beta,17beta) disulfate.

Conclusions

This is the first report of genome-wide significant SNP and related metabolites associated with elite athlete status. Further investigations of the functional relevance of the identified SNPs and metabolites in relation to enhanced athletic performance are warranted.

Alteration of the Dopamine Receptors' Expression in the Cerebellum of the Lysosomal Acid Phosphatase 2 Mutant (Naked-Ataxia (NAX)) Mouse

A spontaneous mutation in the lysosomal acid phosphatase (Acp2) enzyme (nax: naked-ataxia) in experimental mice results in delayed hair appearance and severe cytoarchitectural impairments of the cerebellum, such as a Purkinje cell (PC) migration defect. In our previous investigation, our team showed that Acp2 expression plans a significant role in cerebellar development. On the other hand, the dopaminergic system is also a player in central nervous system (CNS) development, including cerebellar structure and function. In the current investigation, we have explored how Acp2 can be involved in the regulation of the dopaminergic pathway in the cerebellum via the regulation of dopamine receptor expression and patterning. We provided evidence about the distribution of different dopamine receptors in the developing cerebellum by comparing the expression of dopamine receptors on postnatal days (P) 5 and 17 between nax mice and wild-type (wt) littermates. To this aim, immunohistochemistry and Western blot analysis were conducted using five antibodies against dopamine receptors (DRD1, -2, -3, -4, and -5) accompanied by RNAseq data. Our results revealed that DRD1, -3, and -4 gene expressions significantly increased in nax cerebella but not in wt, while gene expressions of all 5 receptors were evident in PCs of both wt and nax cerebella. DRD3 was strongly expressed in the PCs' somata and cerebellar nuclei neurons at P17 in nax mice, which was comparable to the expression levels in the cerebella of wt littermates. In addition, DRD3 was expressed in scattered cells in a granular layer reminiscent of Golgi cells and was observed in the wt cerebella but not in nax mice. DRD4 was expressed in a subset of PCs and appeared to align with the unique parasagittal stripes pattern. This study contributes to our understanding of alterations in the expression pattern of DRDs in the cerebellum of nax mice in comparison to their wt littermates, and it highlights the role of Acp2 in regulating the dopaminergic system.

Genetic diversity and functional effect of common polymorphisms in genes involved in the first heterodimeric complex of the Nucleotide Excision Repair pathway

Nucleotide excision repair is a multistep process that recognizes and eliminates a spectrum of DNA damages. Five proteins, namely XPC, RAD23, Centrin 2, DDB1 and DDB2 act as a heterodimeric complex at the early steps of the NER pathway and play a crucial role in the removal of DNA lesions. Several exonic mutations on genes coding for these proteins have been identified as associated with Xeroderma-pigmentosum (XP), a rare monogenic disorder. However, the role of regulatory polymorphisms in disease development and inter-ethnic diversity is still not well documented. Due to the high incidence rate of XP in Tunisia, we performed a genotyping analysis of 140 SNPs found on these 5 genes in a set of 135-subjects representing the general Tunisian-population. An inter-ethnic comparison based on the genotype frequency of these SNPs have been also conducted. For the most relevant variants, we performed a comprehensive assessment of their functional effects. Linkage disequilibrium and principal component analysis showed that the Tunisian-population is an admixed and intermediate population between Sub-Saharan Africans and Europeans. Using variable factor maps, we identified a list of 20 polymorphisms that contribute considerably to the inter-ethnic diversity of the NER complex. In-silico functional analysis showed that SNPs on XPC, DDB1 and DDB2 are associated with eQTLs mainly DDB2-rs10838681 that seems to decrease significantly the expression level of ACP2 (p = 6.1 × 10^-26). Statistical analysis showed that the allelic frequency of DDB2-rs10838681 in Tunisia is significantly different from all other populations. Using rVarBase, we identified 5 variants on XPC, DDB1 and DDB2 that seem to alter the binding sites of several transcription factors considered as key players in DNA-repair pathways. Results presented in this study provide the first report on regulatory polymorphisms of the NER-complex genes in Tunisia. These results may also help to establish a baseline database for future association and functional studies.

Neuronal Migration During Development of the Cerebellum

Neuronal migration is a fundamental process in central nervous system (CNS) development. The assembly of functioning neuronal circuits relies on neuronal migration occurring in the appropriate spatio-temporal pattern. A defect in the neuronal migration may result in a neurological disorder. The cerebellum, as a part of the CNS, plays a pivotal role in motor coordination and non-motor functions such as emotion, cognition and language. The excitatory and inhibitory neurons within the cerebellum originate from different distinct germinal zones and migrate through complex routes to assemble in a well-defined neuronal organization in the cerebellar cortex and nuclei. In this review article, the neuronal migration modes and pathways from germinal zones to the final position in the cerebellar cortex and nuclei will be described. The cellular and molecular mechanisms involved in cerebellar neuronal migration during development will also be reviewed. Finally, some diseases and animal models associated with defects in neuronal migration will be presented.

Lysosomal acid phosphatase 2 is an unfavorable prognostic factor but is associated with better survival in stage II colorectal cancer patients receiving chemotherapy

Colorectal cancer (CRC) is one of the leading cancers worldwide. Surgery is the main therapeutic modality for stage II CRC. However, the implementation of adjuvant chemotherapy remains controversial and is not universally applied so far. In this study, we found that the protein expression of lysosomal acid phosphatase 2 (ACP2) was increased in CRC and that stage II CRC patients with high ACP2 expression showed a poorer outcome than those with low ACP2 expression (p = 0.004). To investigate this discrepancy, we analyzed the relation between ACP2 expression and several clinical cofactors.

Among patients who received chemotherapy, those with an high expression of ACP2 showed better survival in both stage II and III CRC than those with low ACP2 expression. In stage II CRC patients, univariate analysis showed ACP2 expression and T stage to be cofactors significantly associated with overall survival (ACP2: p = 0.006; T stage: p = 0.034). Multivariate Cox proportion hazard model analysis also revealed ACP2 to be an independent prognostic factor for overall survival (ACP2: p = 0.006; T stage: p = 0.041). Furthermore, ACP2-knockdown CRC cells showed an increase in chemoresistance to 5-FU treatment and increased proliferation marker in the ACP2 knockdown clone.

Taken together, our results suggested that ACP2 is an unfavorable prognostic factor for stage II CRC and may serve as a potential chemotherapy-sensitive marker to help identify a subset of stage II and III CRC patients for whom chemotherapy would improve survival.

Forward Genetic Screen in Caenorhabditis elegans Suggests F57A10.2 and acp-4 As Suppressors of C9ORF72 Related Phenotypes

An abnormally expanded GGGGCC repeat in C9ORF72 is the most frequent causal mutation associated with amyotrophic lateral sclerosis (ALS)/frontotemporal lobar degeneration (FTLD). Both gain-of-function (gf) and loss-of-function (lf) mechanisms have been involved in C9ORF72 related ALS/FTLD. The gf mechanism of C9ORF72 has been studied in various animal models but not in C. elegans. In the present study, we described mutant C9ORF72 modeling in C. elegans and report the finding of two suppressor genes. We made transgenes containing 9 or 29 repeats of GGGGCC in C9ORF72, driven by either the hsp-16 promoters or the unc-119 promoter. Transgenic worms were made to carry such transgenes. Phenotypic analysis of those animals revealed that P_hsp−16::(G4C2)₂₉::GFP transgenic animals (EAB 135) displayed severe paralysis by the second day of adulthood, followed by lethality, which phenotypes were less severe in P_hsp−16::(G4C2)₉::GFP transgenic animals (EAB242), and absent in control strains expressing empty vectors. Suppressor genes of this locomotor phenotype were pursued by introducing mutations with ethyl methanesulfonate in EAB135, screening mutant strains that moved faster than EAB135 by a food-ring assay, identifying mutations by whole-genome sequencing and testing the underlying mechanism of the suppressor genes either by employing RNA interference studies or C. elegans genetics. Three mutant strains, EAB164, EAB165 and EAB167, were identified. Eight suppressor genes carrying nonsense/canonical splicing site mutations were confirmed, among which a nonsense mutation of F57A10.2/VAMP was found in all three mutant strains, and a nonsense mutation of acp-4/ACP2 was only found in EAB164. Knock down/out of those two genes in EAB135 animals by feeding RNAi/introducing a known acp-4 null allele phenocopied the suppression of the C9ORF72 variant related movement defect in the mutant strains. Translational conformation in a mammalian system is required, but our worm data suggest that altering acp-4/ACP2 encoding lysosomal acid phosphatase may provide a potential therapeutic method of reducing acp-4/ACP2 levels, as opposed or complementary to directly reducing C9ORF72, to relieve C9ORF72-ALS phenotypes. It also suggests that the C9ORF72-ALS/FTLD may share a pathophysiologic mechanism with vesicle-associated membrane protein-associated protein B, a homolog of F57A10.2/VAMP, which is a proven ALS8 gene.

Cerebellar Expression of the Neurotrophin Receptor p75 in Naked-Ataxia Mutant Mouse

Spontaneous mutation in the lysosomal acid phosphatase 2 (Acp2) mouse (nax--naked-ataxia mutant mouse) correlates with severe cerebellar defects including ataxia, reduced size and abnormal lobulation as well as Purkinje cell (Pc) degeneration. Loss of Pcs in the nax cerebellum is compartmentalized and harmonized to the classic pattern of gene expression of the cerebellum in the wild type mouse. Usually, degeneration starts in the anterior and posterior zones and continues to the central and nodular zones of cerebellum. Studies have suggested that the p75 neurotrophin receptor (NTR) plays a role in Pc degeneration; thus, in this study, we investigated the p75NTR pattern and protein expression in the cerebellum of the nax mutant mouse. Despite massive Pc degeneration that was observed in the nax mouse cerebellum, p75NTR pattern expression was similar to the HSP25 pattern in nax mice and comparable with wild type sibling cerebellum. In addition, immunoblot analysis of p75NTR protein expression did not show any significant difference between nax and wild type sibling (p > 0.5). In comparison with wild type counterparts, p75NTR pattern expression is aligned with the fundamental cytoarchitecture organization of the cerebellum and is unchanged in the nax mouse cerebellum despite the severe neurodevelopmental disorder accompanied with Pc degeneration.

Transcript Expression Data from Human Islets Links Regulatory Signals from Genome-Wide Association Studies for Type 2 Diabetes and Glycemic Traits to Their Downstream Effectors

The intersection of genome-wide association analyses with physiological and functional data indicates that variants regulating islet gene transcription influence type 2 diabetes (T2D) predisposition and glucose homeostasis. However, the specific genes through which these regulatory variants act remain poorly characterized. We generated expression quantitative trait locus (eQTL) data in 118 human islet samples using RNA-sequencing and high-density genotyping. We identified fourteen loci at which cis-exon-eQTL signals overlapped active islet chromatin signatures and were coincident with established T2D and/or glycemic trait associations. ‎At some, these data provide an experimental link between GWAS signals and biological candidates, such as DGKB and ADCY5. At others, the cis-signals implicate genes with no prior connection to islet biology, including WARS and ZMIZ1. At the ZMIZ1 locus, we show that perturbation of ZMIZ1 expression in human islets and beta-cells influences exocytosis and insulin secretion, highlighting a novel role for ZMIZ1 in the maintenance of glucose homeostasis. Together, these findings provide a significant advance in the mechanistic insights of T2D and glycemic trait association loci.

Cellular commitment in the developing cerebellum

The mammalian cerebellum is located in the posterior cranial fossa and is critical for motor coordination and non-motor functions including cognitive and emotional processes. The anatomical structure of cerebellum is distinct with a three-layered cortex. During development, neurogenesis and fate decisions of cerebellar primordium cells are orchestrated through tightly controlled molecular events involving multiple genetic pathways. In this review, we will highlight the anatomical structure of human and mouse cerebellum, the cellular composition of developing cerebellum, and the underlying gene expression programs involved in cell fate commitments in the cerebellum. A critical evaluation of the cell death literature suggests that apoptosis occurs in ~5% of cerebellar cells, most shortly after mitosis. Apoptosis and cellular autophagy likely play significant roles in cerebellar development, we provide a comprehensive discussion of their role in cerebellar development and organization. We also address the possible function of unfolded protein response in regulation of cerebellar neurogenesis. We discuss recent advancements in understanding the epigenetic signature of cerebellar compartments and possible connections between DNA methylation, microRNAs and cerebellar neurodegeneration. Finally, we discuss genetic diseases associated with cerebellar dysfunction and their role in the aging cerebellum.

Spatial and temporal expression of lysosomal acid phosphatase 2 (ACP2) reveals dynamic patterning of the mouse cerebellar cortex

The Acp2 gene encodes lysosomal acid phosphatase 2 (ACP2), an isoenzyme that hydrolyzes orthophosphoric monoesters to alcohol and phosphate. Mutations in this gene compromise lysosomal function and cause acid phosphatase deficiency. Loss of Acp2 in the brain causes defects in the cerebellum. Here, we performed an in-depth protein expression analysis in the mouse cerebellum to understand how Acp2 controls cellular function in the developing and adult brain. We have found that during development, ACP2 expression marks the caudal midbrain and cerebellum, two regions that are linked by multiple signaling mechanisms during embryogenesis. By around P8, ACP2 was localized predominantly to the somata of Purkinje cells, the principal neurons of the cerebellar cortex. During the second postnatal week, we found that ACP2 expression expanded into the dendrites and axon terminals of Purkinje cells. However, at 2 weeks of age, only a subset of Purkinje cells strongly express ACP2. Further expression analyses revealed that in the mature cerebellum, ACP2 expression divided Purkinje cells into a pattern of molecular zones that are associated with the functional topography of sensory-motor circuitry. These data suggest that ACP2 expression is dynamically regulated during development, and in the adult, it may function within a complex architecture that is linked to cerebellar modular organization.

Mutations in the cholesterol transporter gene ABCA5 are associated with excessive hair overgrowth

Inherited hypertrichoses are rare syndromes characterized by excessive hair growth that does not result from androgen stimulation, and are often associated with additional congenital abnormalities. In this study, we investigated the genetic defect in a case of autosomal recessive congenital generalized hypertrichosis terminalis (CGHT) (OMIM135400) using whole-exome sequencing. We identified a single base pair substitution in the 5' donor splice site of intron 32 in the ABC lipid transporter gene ABCA5 that leads to aberrant splicing of the transcript and a decrease in protein levels throughout patient hair follicles. The homozygous recessive disruption of ABCA5 leads to reduced lysosome function, which results in an accumulation of autophagosomes, autophagosomal cargos as well as increased endolysosomal cholesterol in CGHT keratinocytes. In an unrelated sporadic case of CGHT, we identified a 1.3 Mb cryptic deletion of chr17q24.2-q24.3 encompassing ABCA5 and found that ABCA5 levels are dramatically reduced throughout patient hair follicles. Collectively, our findings support ABCA5 as a gene underlying the CGHT phenotype and suggest a novel, previously unrecognized role for this gene in regulating hair growth.

Purkinje cell compartmentation in the cerebellum of the lysosomal Acid phosphatase 2 mutant mouse (nax - naked-ataxia mutant mouse)

The Acp2 gene encodes the beta subunit of lysosomal acid phosphatase, which is an isoenzyme that hydrolyzes orthophosphoric monoesters. In mice, a spontaneous mutation in Acp2 results in severe cerebellar defects. These include a reduced size, abnormal lobulation, and an apparent anterior cerebellar disorder with an absent or hypoplastic vermis. Based on differential gene expression in the cerebellum, the mouse cerebellar cortex can normally be compartmentalized anteroposteriorly into four transverse zones and mediolaterally into parasagittal stripes. In this study, immunohistochemistry was performed using various Purkinje cell compartmentation markers to examine their expression patterns in the Acp2 mutant. Despite the abnormal lobulation and anterior cerebellar defects, zebrin II and PLCβ4 showed similar expression patterns in the nax mutant and wild type cerebellum. However, fewer stripes were found in the anterior zone of the nax mutant, which could be due to a lack of Purkinje cells or altered expression of the stripe markers. HSP25 expression was uniform in the central zone of the nax mutant cerebellum at around postnatal day (P) 18–19, suggesting that HSP25 immunonegative Purkinje cells are absent or delayed in stripe pattern expression compared to the wild type. HSP25 expression became heterogeneous around P22–23, with twice the number of parasagittal stripes in the nax mutant compared to the wild type. Aside from reduced size and cortical disorganization, both the posterior zone and nodular zone in the nax mutant appeared less abnormal than the rest of the cerebellum. From these results, it is evident that the anterior zone of the nax mutant cerebellum is the most severely affected, and this extends beyond the primary fissure into the rostral central zone/vermis. This suggests that ACP2 has critical roles in the development of the anterior cerebellum and it may regulate anterior and central zone compartmentation.

Potocki-Shaffer deletion encompassing ALX4 in a patient with frontonasal dysplasia phenotype

Frontonasal dysplasia (FND) is a genetically heterogeneous malformation spectrum with marked hypertelorism, broad nasal tip and bifid nose. Only a small number of genes have been associated with FND phenotypes until now, the first gene being EFNB1, related to craniofrontonasal syndrome (CFNS) with craniosynostosis in addition, and more recently the aristaless-like homeobox genes ALX3, ALX4, and ALX1, which have been related with distinct phenotypes named FND1, FND2, and FND3 respectively. We here report on a female patient presenting with severe FND features along with partial alopecia, hypogonadism and intellectual disability. While molecular investigations did not reveal mutations in any of the known genes, ALX4, ALX3, ALX1 and EFNB1, comparative genomic hybridization (array CGH) techniques showed a large heterozygous de novo deletion at 11p11.12p12, encompassing the ALX4 gene. Deletions in this region have been described in patients with Potocki-Shaffer syndrome (PSS), characterized by biparietal foramina, multiple exostoses, and intellectual disability. Although the patient reported herein manifests some overlapping features of FND and PPS, it is likely that the observed phenotype maybe due to a second unidentified mutation in the ALX4 gene. The phenotype will be discussed in view of the deleted region encompassing the ALX4 gene.

The juvenile alopecia mutation (jal) maps to mouse Chromosome 2, and is an allele of GATA binding protein 3 (Gata3)

BACKGROUND

Mice homozygous for the juvenile alopecia mutation (jal) display patches of hair loss that appear as soon as hair develops in the neonatal period and persist throughout life. Although a report initially describing this mouse variant suggested that jal maps to mouse Chromosome 13, our preliminary mapping analysis did not support that claim.

RESULTS

To map jal to a particular mouse chromosome, we produced a 103-member intraspecific backcross panel that segregated for jal, and typed it for 93 PCR-scorable, microsatellite markers that are located throughout the mouse genome. Only markers from the centromeric tip of Chromosome 2 failed to segregate independently from jal, suggesting that jal resides in that region. To more precisely define jal's location, we characterized a second, 374-member backcross panel for the inheritance of five microsatellite markers from proximal Chromosome 2. This analysis restricted jal's position between D2Mit359 and D2Mit80, an interval that includes Il2ra (for interleukin 2 receptor, alpha chain), a gene that is known to be associated with alopecia areata in humans. Complementation testing with an engineered null allele of Il2ra, however, showed that jal is a mutation in a distinct gene. To further refine the location of jal, the 374-member panel was typed for a set of four single-nucleotide markers located between D2Mit359 and D2Mit80, identifying a 0.55 Mb interval where jal must lie. This span includes ten genes-only one of which, Gata3 (for GATA binding protein 3)-is known to be expressed in skin. Complementation testing between jal and a Gata3 null allele produced doubly heterozygous, phenotypically mutant offspring.

CONCLUSIONS

The results presented indicate that the jal mutation is a mutant allele of the Gata3 gene on mouse Chromosome 2. We therefore recommend that the jal designation be changed to Gata3jal, and suggest that this mouse variant may provide an animal model for at least some forms of focal alopecia that have their primary defect in the hair follicle and lack an inflammatory component.

Rhombencephalosynapsis: a hindbrain malformation associated with incomplete separation of midbrain and forebrain, hydrocephalus and a broad spectrum of severity

Rhombencephalosynapsis is a midline brain malformation characterized by missing cerebellar vermis with apparent fusion of the cerebellar hemispheres. Rhombencephalosynapsis can be seen in isolation or together with other central nervous system and extra-central nervous system malformations. Gómez-López-Hernández syndrome combines rhombencephalosynapsis with parietal/temporal alopecia and sometimes trigeminal anaesthesia, towering skull shape and dysmorphic features. Rhombencephalosynapsis can also be seen in patients with features of vertebral anomalies, anal atresia, cardiovascular anomalies, trachea-oesophageal fistula, renal anomalies, limb defects (VACTERL) association. Based on a comprehensive evaluation of neuroimaging findings in 42 patients with rhombencephalosynapsis, we propose a spectrum of severity, ranging from mild (the partial absence of nodulus, anterior and posterior vermis), to moderate (the absence of posterior vermis with some anterior vermis and nodulus present), to severe (the absence of posterior and anterior vermis with some nodulus present), to complete (the absence of the entire vermis including nodulus). We demonstrate that the severity of rhombencephalosynapsis correlates with fusion of the tonsils, as well as midbrain abnormalities including aqueductal stenosis and midline fusion of the tectum. Rhombencephalosynapsis is also associated with multiple forebrain abnormalities including absent olfactory bulbs, dysgenesis of the corpus callosum, absent septum pellucidum and, in rare patients, atypical forms of holoprosencephaly. The frequent association between rhombencephalosynapsis and aqueductal stenosis prompted us to evaluate brain magnetic resonance images in other patients with aqueductal stenosis at our institution, and remarkably, we identified rhombencephalosynapsis in 9%. Strikingly, subjects with more severe rhombencephalosynapsis have more severely abnormal neurodevelopmental outcome, as do subjects with holoprosencephaly and patients with VACTERL features. In summary, our data provide improved diagnostic and prognostic information, and support disruption of dorsal-ventral patterning as a mechanism underlying rhombencephalosynapsis.

Generation of free radicals in haemocytes of mussels after exposure to low molecular weight PAH components: immune activation, oxidative and genotoxic effects

Polycyclic aromatic hydrocarbons (PAHs) constituents, such as phenanthrene (PH) and anthracene (AN), are considered toxic for marine organisms, including bivalve mollusks. The present study showed that the perturbation of health status in mussels, as well as their inability to survive in air (stress on stress response), following exposure to either PH or AN (at a final concentration of 0.1 mg/L respectively), and a mixture of them (ration 1:1, at a final concentration of 0.2 mg/L) for 7 days, is probably related with alterations occurred in their haemocytes. According to the present study, PH and AN, either alone or in a mixture, could induce elevated levels of superoxide anions ((•)O(2)(-)) within haemocytes of mussels, thus leading to immune susceptibility as indicated by the increased levels of cell death and the elevated levels of lysosomal membrane acid phosphatase (AcP) activity, probably occurred via its overproduction or its release into the cytosol after lysosomal membrane destabilisation. PAH-mediated oxidative and genotoxic effects, indicated by the increased levels of both lipid peroxidation (MDA content) and nuclear abnormalities (MN test) could be related with haemocytes' inability to overcome free radical generation, thus leading to attenuation of general health status, before other disturbances, such as death, occur.

Multi-system disorders of glycosphingolipid and ganglioside metabolism

Glycosphingolipids (GSLs) and gangliosides are a group of bioactive glycolipids that include cerebrosides, globosides, and gangliosides. These lipids play major roles in signal transduction, cell adhesion, modulating growth factor/hormone receptor, antigen recognition, and protein trafficking. Specific genetic defects in lysosomal hydrolases disrupt normal GSL and ganglioside metabolism leading to their excess accumulation in cellular compartments, particularly in the lysosome, i.e., lysosomal storage diseases (LSDs). The storage diseases of GSLs and gangliosides affect all organ systems, but the central nervous system (CNS) is primarily involved in many. Current treatments can attenuate the visceral disease, but the management of CNS involvement remains an unmet medical need. Early interventions that alter the CNS disease have shown promise in delaying neurologic involvement in several CNS LSDs. Consequently, effective treatment for such devastating inherited diseases requires an understanding of the early developmental and pathological mechanisms of GSL and ganglioside flux (synthesis and degradation) that underlie the CNS diseases. These are the focus of this review.

RAB26 and RAB3D are direct transcriptional targets of MIST1 that regulate exocrine granule maturation

Little is known about how differentiating cells reorganize their cellular structure to perform specialized physiological functions. MIST1, an evolutionarily conserved transcription factor, is required for the formation of large, specialized secretory vesicles in gastric zymogenic (chief) cells (ZCs) as they differentiate from their mucous neck cell progenitors. Here, we show that MIST1 binds to highly conserved CATATG E-boxes to directly activate transcription of 6 genes, including those encoding the small GTPases RAB26 and RAB3D. We next show that RAB26 and RAB3D expression is significantly downregulated in Mist1(-)(/)(-) ZCs, suggesting that MIST1 establishes large secretory granules by inducing RAB transcription. To test this hypothesis, we transfected human gastric cancer cell lines stably expressing MIST1 with red fluorescent protein (RFP)-tagged pepsinogen C, a key secretory product of ZCs. Those cells upregulate expression of RAB26 and RAB3D to form large secretory granules, whereas control, non-MIST1-expressing cells do not. Moreover, granule formation in MIST1-expressing cells requires RAB activity because treatment with a RAB prenylation inhibitor and transfection of dominant negative RAB26 abrogate granule formation. Together, our data establish the molecular process by which a transcription factor can directly induce fundamental cellular architecture changes by increasing transcription of specific cellular effectors that act to organize a unique subcellular compartment.

Specific saposin C deficiency: CNS impairment and acid beta-glucosidase effects in the mouse

Saposins A, B, C and D are derived from a common precursor, prosaposin (psap). The few patients with saposin C deficiency develop a Gaucher disease-like central nervous system (CNS) phenotype attributed to diminished glucosylceramide (GC) cleavage activity by acid β-glucosidase (GCase). The in vivo effects of saposin C were examined by creating mice with selective absence of saposin C (C−/−) using a knock-in point mutation (cysteine-to-proline) in exon 11 of the psap gene. In C−/− mice, prosaposin and saposins A, B and D proteins were present at near wild-type levels, but the saposin C protein was absent. By 1 year, the C−/− mice exhibited weakness of the hind limbs and progressive ataxia. Decreased neuromotor activity and impaired hippocampal long-term potentiation were evident. Foamy storage cells were observed in dorsal root ganglion and there was progressive loss of cerebellar Purkinje cells and atrophy of cerebellar granule cells. Ultrastructural analyses revealed inclusions in axonal processes in the spinal cord, sciatic nerve and brain, but no excess of multivesicular bodies. Activated microglial cells and astrocytes were present in thalamus, brain stem, cerebellum and spinal cord, indicating regional pro-inflammatory responses. No storage cells were found in visceral organs of these mice. The absence of saposin C led to moderate increases in GC and lactosylceramide (LacCer) and their deacylated analogues. These results support the view that saposin C has multiple roles in glycosphingolipid (GSL) catabolism as well as a prominent function in CNS and axonal integrity independent of its role as an optimizer/stabilizer of GCase.

Time-course study of the early lysosomal responses to pollutants in mussel digestive cells using acid phosphatase as lysosomal marker enzyme

Lysosomal biomarkers are early warning signals of the biological effects caused by environmental pollutants but the promptness of lysosomal responses to pollutants has not been investigated yet. This work is aimed to determine the response-time of digestive cell lysosomes in mussels exposed to metals and hydrocarbons. Mussels, Mytilus galloprovincialis, were exposed, under laboratory conditions to Cd and to the water-accommodated fraction of a lubricant oil. One mussel per experimental group was sacrificed and processed every hour from 0 h to 30 h. Changes in AcP activity, immunoreactivity and LMS test based on AcP histochemistry, discriminates significantly control and exposed mussels within 5 h exposure. The present results suggested that after 15-20 h exposure digestive cell loss might be accompanied by increased AcP activity (extralysosomal) without a parallel increase in the levels of immunoreactive AcP protein, especially after Cd-exposure. The reduced labilisation period of lysosomal membrane constitute a cost effective early warning signal that, however, is not necessarily correlated with the exposure time. The routine application of immunochemical techniques deserves more research efforts before its implementation although, these techniques are very valuable to understand and interpret correctly lysosomal responses to pollutants.

Gomez-Lopez-Hernandez syndrome: two new cases and review of the literature

Gomez-Lopez-Hernandez syndrome, or cerebellotrigeminal-dermal dysplasia, is a rare neurocutaneous syndrome of trigeminal anesthesia, scalp alopecia and cerebellar anomalies. Other features include craniosynostosis, short stature, hypertelorism, down-slanting palpebral fissures, corneal opacities, mediofacial hypoplasia, and turri-brachycephaly. There have been 19 cases documented to date and we report on two additional male patients, 1 and 6 years of age, with typical features, mild mental retardation and dyspraxia. In both cases, MRI findings included rhombencephalosynapsis, a constant neuroimaging feature in this syndrome, comprising fusion of the cerebellar hemispheres with agenesis of the cerebellar vermis. Based on literature and our experience, we propose the presence of trigeminal anesthesia and/or partial alopecia of the scalp to complete the diagnosis of the syndrome.

Two new Brazilian patients with Gómez-López-Hernández syndrome: reviewing the expanded phenotype with molecular insights

Gómez-López-Hernández (GLH) syndrome or cerebello-trigeminal dysplasia is a neurocutaneous syndrome whose etiology is unknown at the present time. We report two additional Brazilian patients, including the oldest one known to date (age 29). Here, we review the expanded phenotype in four patients with new clinical, psychiatric, radiological, and molecular investigations. One patient may have hypomania within the bipolar spectrum disorder with onset in childhood and adolescence. Primary growth hormone (GH) deficiency was ruled out in all patients, although one of them might have developed secondary GH deficiency due to partial hypopituitarism following severe hydrocephalus. Brain magnetic resonance angiography disclosed no azygous anterior cerebral artery (ACA) but only normal variants. Molecular analysis of the lysosomal acid phosphatase gene (ACP2) was performed, but no pathogenic mutations were identified. We present an overview of the phenotypic features of all patients described to date. There are currently 12 unrelated patients reported in the literature, 5 of whom are Brazilian. We discuss new molecular insights and speculate about the pathogenesis of GLH syndrome.

Gomez-Lopez-Hernandez syndrome: an easily missed diagnosis

Gomez-Lopez-Hernandez syndrome (GLHS) is a rare syndrome comprising the triad rhombencephalosynapsis (RS), parietal alopecia, and trigeminal anesthesia. Other typical findings are skull abnormalities, craniofacial dysmorphic signs, and short stature. Intellectual impairment is typical but cases with normal cognitive functions have also been reported. Only 15 cases of GLHS have been described so far, all sporadic. We report four further patients with GLHS: one neonate, two children and a middle aged man. In all cases the diagnosis was made only in retrospect; one child died as neonate due to esophageal atresia. All patients presented RS and parietal alopecia, three intermittent head stereotypies, two had obvious trigeminal anesthesia, and one normal cognition. Alopecia and also trigeminal anesthesia can be very mild and can be easily missed. However, the dysmorphic signs including bilateral alopecia are already present in the neonatal period and are highly suggestive of GLHS. RS should be looked for in this situation. It is important to mention that neuroimaging does not allow distinguishing between isolated RS and GLHS. If RS is diagnosed the clinical signs of GLHS should be sought. The diagnosis of GLHS can only be made by the combination of the typical dysmorphic signs and neuroimaging in the neonatal period, but not prenatally.

Identification of a novel risk locus for progressive supranuclear palsy by a pooled genomewide scan of 500,288 single-nucleotide polymorphisms

To date, only the H1 MAPT haplotype has been consistently associated with risk of developing the neurodegenerative disease progressive supranuclear palsy (PSP). We hypothesized that additional genetic loci may be involved in conferring risk of PSP that could be identified through a pooling-based genomewide association study of >500,000 SNPs. Candidate SNPs with large differences in allelic frequency were identified by ranking all SNPs by their probe-intensity difference between cohorts. The MAPT H1 haplotype was strongly detected by this methodology, as was a second major locus on chromosome 11p12-p11 that showed evidence of association at allelic (P<.001), genotypic (P<.001), and haplotypic (P<.001) levels and was narrowed to a single haplotype block containing the DNA damage-binding protein 2 (DDB2) and lysosomal acid phosphatase 2 (ACP2) genes. Since DNA damage and lysosomal dysfunction have been implicated in aging and neurodegenerative processes, both genes are viable candidates for conferring risk of disease.

Basis of lethality in C. elegans lacking CUP-5, the Mucolipidosis Type IV orthologue

Mutations in MCOLN1, which encodes the protein h-mucolipin-1, result in the lysosomal storage disease Mucolipidosis Type IV. Studies on CUP-5, the human orthologue of h-mucolipin-1 in Caenorhabditis elegans, have shown that these proteins are required for lysosome biogenesis. We show here that the lethality in cup-5 mutant worms is due to two defects, starvation of embryonic cells and general developmental defects. Starvation leads to apoptosis through a CED-3-mediated pathway. We also show that providing worms with a lipid-soluble metabolite partially rescues the embryonic lethality but has no effect on the developmental defects, the major cause of the lethality. These results indicate that supplementing the metabolic deficiency of Mucolipidosis Type IV patients mat not be sufficient to alleviate the symptoms due to tissue degeneration.

Prenatal magnetic resonance imaging in Gomez-Lopez-Hernandez syndrome and review of the literature

Gomez-Lopez-Hernandez syndrome, or cerebello-trigeminal-dermal dysplasia (OMIM#601853), is a rare syndrome comprising cerebellar abnormalities, parieto-occipital alopecia, trigeminal nerve anesthesia, intellectual impairment, craniosynostosis, short stature, and craniofacial anomalies. It has been reported in ten patients, five of whom are Brazilian. Rhombencephalosynapsis is a rare sporadic cerebellar anomaly comprising fusion of the cerebellar hemispheres with agenesis of the cerebellar vermis. Rhombencephalosynapsis is a constant feature of Gomez-Lopez-Hernandez syndrome. We present the clinical and imaging findings of a Caucasian male infant with Gomez-Lopez-Hernandez syndrome. Rhombencephalosynapsis was diagnosed with fetal magnetic resonance imaging (MRI) after an abnormally shaped small cerebellum was detected by antenatal ultrasound (US). Gomez-Lopez-Hernandez syndrome was diagnosed at age 6 weeks when parietal alopecia was noted. Prenatal imaging studies of Gomez-Lopez-Hernandez syndrome have not been published before. When rhombencephalosynapsis is diagnosed prenatally, the clinical features of Gomez-Lopez-Hernandez syndrome should be sought at postnatal review. Gomez-Lopez-Hernandez syndrome and isolated rhombencephalosynapsis may have a common etiology.