The effect of opting-in versus opting-out forming on the rate of reported variants of questionable significance in prenatal microarray.

OBJECTIVE: To examine the effect of patient-selected opt-in versus opt-out option on the rate of reported variants of uncertain clinical significance (VOUS) and high-frequency low-penetrant (HFLP) findings in prenatal microarray testing. METHODS: A standard microarray consent form in Israel includes a requirement to note patient choice to be or not to be informed about the presence of VOUS and HFLP variants. The original form was designed as an opting-out method, in which the women had to actively mark if they did not want to be informed about questionable findings. In the authors' Genetic Institute, the form was changed for an opting-in option in October 2019. In this study we have compared the rates of reported VOUS and HFLP variants between the opt-in and opt-out periods. RESULTS: Of the 1014 prenatal CMA tests, 590 (58.2%) were performed in the opt-out period. A significant decrease in the rate of women requesting to be informed of VOUS findings was noted (66.8% in opt-out period vs 34.0% in opt-in period), yielding a relative risk (RR) of 0.46 (95% confidence interval [CI] 0.39-0.53). Rate of women preferring to be informed of HFLP variants decreased from 75.3% to 48.1% (RR 0.52, 95% CI 0.45-0.60). DISCUSSION: We present a simple and effective method to decrease the rate of reported findings of questionable significance in the prenatal setting. These results are important not only for microarray results, but also for next-generation sequencing techniques, such as whole exome or genome sequencing.

Drosophila melanogaster Mutated in its GBA1b Ortholog Recapitulates Neuronopathic Gaucher Disease.

Gaucher disease (GD) results from mutations in the GBA1 gene, which encodes lysosomal glucocerebrosidase (GCase). The large number of mutations known to date in the gene lead to a heterogeneous disorder, which is divided into a non-neuronopathic, type 1 GD, and two neurological, type 2 and type 3, forms. We studied the two fly GBA1 orthologs, GBA1a and GBA1b. Each contains a Minos element insertion, which truncates its coding sequence. In the GBA1am/m flies, which express a mutant protein, missing 33 C-terminal amino acids, there was no decrease in GCase activity or substrate accumulation. However, GBA1bm/m mutant flies presented a significant decrease in GCase activity with concomitant substrate accumulation, which included C14:1 glucosylceramide and C14:0 glucosylsphingosine. GBA1bm/m mutant flies showed activation of the Unfolded Protein Response (UPR) and presented inflammation and neuroinflammation that culminated in development of a neuronopathic disease. Treatment with ambroxol did not rescue GCase activity or reduce substrate accumulation; however, it ameliorated UPR, inflammation and neuroinflammation, and increased life span. Our results highlight the resemblance between the phenotype of the GBA1bm/m mutant fly and neuronopathic GD and underlie its relevance in further GD studies as well as a model to test possible therapeutic modalities.

The contribution of mutant GBA to the development of Parkinson disease in Drosophila.

Gaucher disease (GD) results from mutations in the acid ß-glucocerebrosidase (GCase) encoding gene, GBA, which leads to accumulation of glucosylceramides. GD patients and carriers of GD mutations have a significantly higher propensity to develop Parkinson disease (PD) in comparison to the non-GD population. In this study, we used the fruit fly Drosophila melanogaster to show that development of PD in carriers of GD mutations results from the presence of mutant GBA alleles. Drosophila has two GBA orthologs (CG31148 and CG31414), each of which has a minos insertion, which creates C-terminal deletion in the encoded GCase. Flies double heterozygous for the endogenous mutant GBA orthologs presented Unfolded Protein Response (UPR) and developed parkinsonian signs, manifested by death of dopaminergic cells, defective locomotion and a shorter life span. We also established transgenic flies carrying the mutant human N370S, L444P and the 84GG variants. UPR activation and development of parkinsonian signs could be recapitulated in flies expressing these three mutant variants.UPR and parkinsonian signs could be partially rescued by growing the double heterozygous flies, or flies expressing the N370S or the L444P human mutant GCase variants, in the presence of the pharmacological chaperone ambroxol, which binds and removes mutant GCase from the endoplasmic reticulum (ER). However flies expressing the 84GG mutant, that does not express mature GCase, did not exhibit rescue by ambroxol. Our results strongly suggest that the presence of a mutant GBA allele in dopaminergic cells leads to ER stress and to their death, and contributes to development of PD.