Patient centered guidelines for the laboratory diagnosis of Gaucher disease type 1

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder due to the deficient activity of the acid beta-glucosidase (GCase) enzyme, resulting in the progressive lysosomal accumulation of glucosylceramide (GlcCer) and its deacylated derivate, glucosylsphingosine (GlcSph). GCase is encoded by the GBA1 gene, located on chromosome 1q21 16 kb upstream from a highly homologous pseudogene. To date, more than 400 GBA1 pathogenic variants have been reported, many of them derived from recombination events between the gene and the pseudogene. In the last years, the increased access to new technologies has led to an exponential growth in the number of diagnostic laboratories offering GD testing. However, both biochemical and genetic diagnosis of GD are challenging and to date no specific evidence-based guidelines for the laboratory diagnosis of GD have been published. The objective of the guidelines presented here is to provide evidence-based recommendations for the technical implementation and interpretation of biochemical and genetic testing for the diagnosis of GD to ensure a timely and accurate diagnosis for patients with GD worldwide. The guidelines have been developed by members of the Diagnostic Working group of the International Working Group of Gaucher Disease (IWGGD), a non-profit network established to promote clinical and basic research into GD for the ultimate purpose of improving the lives of patients with this disease. One of the goals of the IWGGD is to support equitable access to diagnosis of GD and to standardize procedures to ensure an accurate diagnosis. Therefore, a guideline development group consisting of biochemists and geneticists working in the field of GD diagnosis was established and a list of topics to be discussed was selected. In these guidelines, twenty recommendations are provided based on information gathered through a systematic review of the literature and two different diagnostic algorithms are presented, considering the geographical differences in the access to diagnostic services. Besides, several gaps in the current diagnostic workflow were identified and actions to fulfill them were taken within the IWGGD. We believe that the implementation of recommendations provided in these guidelines will promote an equitable, timely and accurate diagnosis for patients with GD worldwide.

Altered localization and functionality of TAR DNA Binding Protein 43 (TDP-43) in niemann- pick disease type C

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized by the occurrence of visceral and neurological symptoms. At present, the molecular mechanisms causing neurodegeneration in this disease are unknown. Here we report the altered expression and/or mislocalization of the TAR-DNA binding protein 43 (TDP-43) in both NPC mouse and in a human neuronal model of the disease. We also report the neuropathologic study of a NPC patient’s brain, showing that while TDP-43 is below immunohistochemical detection in nuclei of cerebellar Purkinje cells, it has a predominant localization in the cytoplasm of these cells. From a functional point of view, the TDP-43 mislocalization, that occurs in a human experimental neuronal model system, is associated with specific alterations in TDP-43 controlled genes. Most interestingly, treatment with N-Acetyl-cysteine (NAC) or beta-cyclodextrin (CD) can partially restore TDP-43 nuclear localization. Taken together, the results of these studies extend the role of TDP-43 beyond the Amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD)/Alzheimer disease (AD) spectrum. These findings may open novel research/therapeutic avenues for a better understanding of both NPC disease and the TDP-43 proteinopathy disease mechanism.

Niemann-Pick Type C-2 Disease: Identification by Analysis of Plasma Cholestane-3β,5α,6β-Triol and Further Insight into the Clinical Phenotype

INTRODUCTION

Niemann-Pick type C disease is a rare disorder caused by impaired intracellular lipid transport due to mutations in either the NPC1 or the NPC2 gene. Ninety-five % of NPC patients show mutations in the NPC1 gene. A much smaller number of patients suffer from NPC2 disease and present respiratory failure as one of the most frequent symptoms. Several plasma oxysterols are highly elevated in NPC1 and can be used as a biomarker in the diagnosis of NPC1.

METHODS

Plasma cholestane-3β,5α,6β-triol was evaluated as biomarker for NPC2 by GC/MS and LC-MS/MS analysis. The diagnosis was confirmed by Sanger sequencing and filipin staining.

RESULTS

We report three NPC2 patients with typical respiratory problems and a detailed description of the nature of the lung disease in one of them. All patients had elevated levels of plasma cholestane-3β,5α,6β-triol. In two of these patients, the positive oxysterol result led to a rapid diagnosis of NPC2 by genetic analysis. The phenotype of the third patient has been described previously. In this patient a cholestane-3β,5α,6β-triol concentration markedly above the reference range was found.

CONCLUSIONS

Measurement of plasma cholestane-3β,5α,6β-triol enables to discriminate between controls and NPC1 and NPC2 patients, making it a valuable biomarker for the rapid diagnosis not only for NPC1 but also for NPC2 disease.The measurement of oxysterols should be well kept in mind in the differential diagnosis of lysosomal diseases, as the elevation of oxysterols in plasma may speed up the diagnosis of NPC1 and NPC2.

Cholesterol metabolism-associated molecules in late onset Alzheimer's disease

Alzheimer’s disease (AD) is the most common cause of dementia and, with an aging population, poses a huge public health problem. Although a small per cent is caused by single gene changes, most AD is sporadic and unexplained. Of many modifying factors, changes in brain cholesterol homeostasis are the best studied. We present a review of the role of altered cholesterol metabolism and hypercholesterolemia in APP processing and Abeta generation. We also provide an overview of the potential pharmacological modulation of cholesterol homeostasis in the brain by cholesterol-lowering agents and beta-cyclodextrins.

Mutation profile of theGAA gene in 40 Italian patients with late onset glycogen storage disease type II

Glycogen storage disease type II (GSDII) is a recessively inherited disorder due to the deficiency of acid alpha-glucosidase (GAA) that results in impaired glycogen degradation and its accumulation in the lysosomes. We report here the complete molecular analysis of the GAA gene performed on 40 Italian patients with late onset GSDII. Twelve novel alleles have been identified: missense mutations were functionally characterized by enzyme activity and protein processing in a human GAA-deficient cell line while splicing mutations were studied by RT-PCR and in silico analysis. A complex allele was also identified carrying three different alterations in cis. The c.-32-13T > G was the most frequent mutation, present as compound heterozygote in 85% of the patients (allele frequency 42.3%), as described in other late onset GSDII Caucasian populations. Interestingly, the c.-32-13T > G was associated with the c.2237G > A (p.W746X) in nine of the 40 patients. Genotype-phenotype correlations are discussed with particular emphasis on the subgroup carrying the c.-32-13T > G/c.2237G > A genotype.

Acid sphingomyelinase: identification of nine novel mutations among Italian Niemann Pick type B patients and characterization of in vivo functional in-frame start codon

Niemann Pick disease (NPD) is an autosomal recessive disorder due to the deficit of lysosomal acid sphingomyelinase, which results in intracellular accumulation of sphingomyelin. In the present work we studied 18 patients with NPD type B, including five individuals who presented an intermediate phenotype characterised by different levels of neurological involvement. We identified nine novel mutations in the SMPD1 gene including six single base changes c.2T>G, c.96G>A, c.308T>C, c.674T>C, c.732G>C, c.841G>A (p.M1_W32del, p.W32X, p.L103P, p.L225P, p.W244C, p.A281T) and three frameshift mutations c.100delC, c.565dupC, c.575dupC (p.G34fsX42, p.P189fsX1 and p.P192fsX14). The novel c.2T>G (p.M1_W32del) mutation inactivates the first in-frame translation start site of the SMPD1 gene and in the homozygous status causes NPD type B indicating that in'vivo translation of wild type SMPD1 initiates from the first in-frame ATG. Moreover, the new c.96G>A (p.W32X) introduces a premature stop codon before the second in-frame ATG. As a consequence of either c.2T>G (p.M1_W32del) or c.96G>A (p.W32X), impaired translation from the first in-frame ATG results in a mild NPD-B phenotype instead of the severe phenotype expected for a complete deficiency of the enzyme, suggesting that when the first ATG is not functional, the second initiation codon (ATG33) still produces a fairly functional sphingomyelinase. Analysis of the patients'clinical and molecular data demonstrated that all five patients with the intermediate phenotype carried at least one severe mutation. No association between the onset of pulmonary symptoms and genotype was observed. Finally, the presence of c.96G>A (p.W32X), the most frequent allele among Italian NPD type B population, and c.1799G>C (p.R600P) as compound heterozygotes in association with severe mutations suggested a beneficial effect for both mutations.

[Molecular analysis of the most frequent mutations associated with congenital adrenal hyperplasia secondary to 21-hydroxylase enzyme deficiency]

Most cases (90%) of congenital adrenal hyperplasia (CAH) are secondary to steroid 21-hydroxylase enzyme deficiency (P450c21). In human, the P450c21 gene (CYP21B) is present along with a non functional pseudogene (CYP21A). These genes, located in chromosome 6, present a sequence homology of 98%. This high homology and the complexity of this gene locus brings about considerable difficulties in its molecular analysis and in the interpretation of the results. The aim of the present study was to elaborate an adequate strategy for the analysis of the most frequent mutations described in the CYP21B gene. A total of 77 patients with clinical and biochemical diagnosis of CAH secondary to P450c21 enzyme deficiency, as well as 170 unaffected relatives, were studied. They belonged to 73 unrelated families (146 chromosomes). The strategy allowed for the differentiation of patients with homozygous point mutations (PM), with PM in one allele and deletions, conversions, Ex3 or Cluster Ex6 PM in the other, even though parents were not always available for the study. Furthermore, it allowed for the discrimination of heterozygous deletions or conversions of the CYP21B gene from duplications of the non functional gene CYP21A, as well as CYP21B and A deletions from normal copies of the two genes. An exhaustive molecular analysis of this gene is necessary for an adequate characterization of the alterations present in this locus.

Expression of the aromatase gene in the human prepubertal testis

It has been proposed that estrogens might play a negative feedback role in the local regulation of androgen biosynthesis in the testis. Although aromatase has been reported to be present in human adult Leydig cells, CYP19 gene expression in the human prepubertal testis has not been studied. Human prepubertal testicular tissue was obtained from 12 testes collected at necropsy. Ages ranged from 0.07 to 7 years, but 7 of the 12 subjects were younger than 3 months old. Tissue mRNA was subjected to RT-PCR analysis by two methods. Cytochrome P450arom mRNA was detected by non-radioactive RT-PCR in five of the 12 prepubertal testes collected from 0.05-7 year-old subjects, and in one testis collected from a 15 year-old pubertal control. Four of these five prepubertal samples belonged to the youngest infant group. Using a more sensitive, radioactive RT-PCR, aromatase mRNA was detected in all prepubertal testes. This study shows that the CYP19 gene is expressed in the prepubertal human testis including the period of early postnatal activation. It is possible that estrogens may have a role in prepubertal males during this period.

Transcriptional regulatory elements of the human gene for cytochrome P450c21 (steroid 21-hydroxylase) lie within intron 35 of the linked C4B gene

The CYP21 gene, which encodes P450c21, the adrenal steroid 21-hydroxylase needed for glucocorticoid synthesis, lies in the major histocompatibility locus only 2.3 kilobase pairs (kb) downstream from the C4 gene. A 300-base pair (bp) proximal promoter and two upstream regions within C4 are needed for expression of mouse CYP21; the human gene also has a proximal promoter, but upstream elements have not been studied. To search for upstream regulatory elements in human CYP21B, we examined up to 9 kb of 5'-flanking DNA by transient transfection into human adrenal NCI-H295A cells. The 300-bp proximal promoter had substantial activity, but constructs retaining the DNA between -4.6 and -5.6 kb had increased activity, indicating the presence of distal elements. This region does not correspond to the mouse upstream regions, lying further upstream within intron 35 of C4B, which encompasses the previously described "Z promoter." DNase I footprinting located two elements, F1 and F2, lying -186 to -195 bp and -142 to -151 bp upstream from the Z cap site (-4862 to -4871 and -4818 to -4827 bp upstream of the CYP21B cap site). Each element formed a specific DNA-protein complex and conferred orientation-independent expression to a heterologous promoter. Mutations abolished formation of the DNA-protein complexes but only partially decreased expression. We identified a third site, F3, lying at -33 to -42 bp from Z. Competitive gel mobility supershift assays and co-transfection studies with SF-1 produced in vitro indicate F2 and F3 bind SF-1; BLAST searches and Southwestern blotting suggest that NF-W2 may bind F1. These results indicate that the Z promoter is a component of the CYP21 promoter needed to drive its adrenal-specific expression and that CYP21 transcription elements within C4 have kept these two genes linked during evolution.

[Role of 3 beta hydroxysteroid dehydrogenase (3 beta HSD) in human adrenal androgen synthesis]

Adrenarche is the maturational increase of adrenal androgens that takes place in 6-8 year old children. In order to study the role of 3 beta HSD in the regulation of the synthesis of human adrenal androgens, the abundance of 3 beta HSD mRNA (Dot Blot and semiquantitative RT-PCR) was measured in 11 human prepubertal and early pubertal adrenal tissues. Subjects were divided in 2 age groups (Gr): Gr1, < 8 years (y) old (n = 6, range 0.1-2.5) and Gr2, > or = 8 y old (n = 5, range 8.0-13.0). Tissue from one adrenal tumor with Cushing's syndrome (TSC) and 2 virilizing adrenal tumors (TV), as well as adrenal cells prepared from the TSC and from 1 TV were also studied. They were maintained in culture for 3 days in basal conditions (BC) and under ACTH and IGF-1 stimulation. mRNA in Gr1 was higher than in Gr2 (Dot blot: 4.65 +/- 2.70 and 0.28 +/- 0.27 AU, p = 0.006; RT-PCR: 21.5 +/- 12.5 and 6.77 +/- 3.78 AU, p = 0.039, respectively). 3 beta HSD mRNA in TSC (8.74 +/- 1.74) was higher than in the 2 TVs (0.47 +/- 0.02 and 0.87 +/- 0.08) p = 0.001. In TSC cells, basal mRNA (0.82 +/- 0.10) decreased under ACTH (0.55 +/- 0.06), p = 0.005, and increased under IGF-1 (2.36 +/- 0.07), p = 0.006. No changes were observed in TV cells. On day 3, TV cells in BC secreted 1170.0 +/- 210.0 and 335.0 +/- 29.0 pmol/10(6) cells in 24 hs of DHEAS and androstenedione, while TSC cells secreted 17.1 +/- 3.5 and 73.7 +/- 11.7, respectively. Values increased under ACTH in TV cells (2006.0 +/- 360.0 and 525.0 +/- 76.0) and in TSC cells (29.8 +/- 5.4 and 366.8 +/- 129) p < 0.05, but they decreased under IGF-1 only in TSC cells (7.9 +/- 2.4 and 43.7 +/- 6.1) p < 0.05. These data support the hypothesis that human adrenarche could be secondary to a decrease of 3 beta HSD mRNA. Our finding that when 3 beta HSD mRNA decreases androgen secretion increases (ACTH) and when 3 beta HSD mRNA increases androgen secretion decreases (IGF-1), strongly suggests that 3 beta HSD has a modulatory role in adrenal androgen steroidogenesis.

Decrease in the expression of the 3beta-hydroxysteroid dehydrogenase gene in human adrenal tissue during prepuberty and early puberty: implications for the mechanism of adrenarche

Adrenarche is the increase of adrenal androgen secretion, mainly dehydroepiandrosterone and dehydroepiandrosterone sulfate, that occurs during prepuberty in higher primates. This event takes place at about 6-8 y of age in humans. It had been postulated that adrenarche might reflect an increase in the 17,20 lyase:17OH-ase activity ratio of microsomal cytochrome P450c17. However, studies to demonstrate this mechanism have been unsuccessful. Because it has been described that virilizing adrenocortical carcinomas have high dehydroepiandrosterone sulfate secretion and low 3beta-hydroxysteroid dehydrogenase (3betaHSD) activity, in this study we evaluated the possible existence of maturative changes of the level of 3betaHSD type II mRNA in 11 normal prepubertal and early pubertal human adrenals. Adrenal glands from subjects aged 0.1 to 13 y were obtained from organ donors, patients undergoing resection of the kidney for renal neoplasms or necropsies with less than 6 h of postmortem time. The expression of 3betaHSD type II gene was studied by dot blot in all samples and by relative reverse transcriptase (RT)-PCR in nine samples. The size of the transcripts was evaluated by Northern blot. Hybridization was performed using labeled human 3betaHSD cDNA probes. The uniformity of loading was tested using labeled human beta actine cDNA. The relative intensities of hybridization signals were quantified by scanning densitometry. The expected bands after relative RT-PCR were eluted, and radioactivity was measured in a scintillation counter. For the analysis of the results, subjects were divided into two groups as a function of age: group 1, less than 8 y (n = 6; range 0.1-2.48 y) and group 2, equal or older than 8 y (n = 5; range 8-13 y). 3BetaHSD type II mRNA expression, analyzed by dot blot and relative RT-PCR, was significantly higher (p < 0.05) in group 1 (median and range 4.99, 0.50-8.00 and 16.3, 13.5-40.0 arbitrary units, respectively) than in group 2 (0.15, 0.12-0.75 and 5.66, 3.18-13.0, respectively). In conclusion, we have shown a decrease of the expression 3betaHSD type II gene as a function of age in prepubertal and early pubertal normal human adrenal tissue. This maturative change might be involved in the mechanism of human adrenarche.

Mutations of the steroid 21-hydroxylase gene in an Argentinian population of 36 patients with classical congenital adrenal hyperplasia

In several studies carried out in USA and Europe, gene deletions, large gene conversions and six point mutations accounted for over 90% of the mutated alleles reported in classical congenital hyperplasia (CAH). In order to know the relative frequencies of mutations in a Latin-American population, the CYP21 active gene was analyzed in 42 patients with CAH belonging to 36 families attending two Argentinian clinics. The salt wasting form was diagnosed in 24 index cases and the simple virilized form in 12. When available, parents were also studied. DNA was extracted from peripheral blood leukocytes and specific PCR amplification of four different fragments of the CYP21 gene was carried out, followed by electrophoresis of the amplified product. The four fragments include segments of the gene containing the six most frequently reported abnormalities in classical CAH: IN2, EX3, R356W, cluster EX6 and I172N. Point mutations were studied by allelic specific oligonucleotide hybridization; Q318X was studied by digestion of the PCR product with PsT1 restriction enzyme and electrophoresis on 6% non-denaturing polyacrylamide gels. Deletions and macroconversions as well as confirmation of homozygote point mutations were studied by Southern blotting. Percentage distribution of abnormalities was as follows: deletion/macroconversion 18, IN2 18, I172N 15.3, Q318X 13.8, R356W 5.5, EX3 2.7, cluster EX6 0, not characterized 26.7. The complete genotype could be determined in 20 families while in 12 additional ones, the mutation was detected in one allele. Deletion/macroconversion, IN2, EX3 and Q318X were detected more frequently in salt wasting patients while I172N and R356W were found in simple virilized patients. However, genotype was not always concordant with phenotype. It is concluded that there are differences in the frequency of several gene mutations and in that of deletion/macroconversion between this Latin-American population and several reported American and European populations. In particular the percentage of deletion/macroconversion, IN2, EX3 and cluster EX6 was lower while I172N was higher in our Latin-American population. Furthermore the frequency of mutations not characterized was larger. This information is useful to delineate appropriate strategies for prenatal diagnosis in this particular population.

Report of an XX male with hypospadias and pubertal gynecomastia, SRY gene negative in blood leukocytes but SRY gene positive in testicular cells

Most XX male subjects present an anomalous translocation of the sex-determining region of the chromosome Y (SRY) gene from chromosome Y to chromosome X. Several explanations have been proposed for the differentiation of testicular tissue in the absence of SRY gene. A patient is presented in whom the SRY gene was absent in peripheral leukocytes but present in testicular tissue. This possibility should always be ruled out before diagnosing Y-negative XX maleness.