A drug repurposing screen reveals dopamine signaling as a critical pathway underlying potential therapeutics for the rare disease DPAGT1-CDG.

DPAGT1-CDG is a Congenital Disorder of Glycosylation (CDG) that lacks effective therapies. It is caused by mutations in the gene DPAGT1 which encodes the first enzyme in N-linked glycosylation. We used a Drosophila rough eye model of DPAGT1-CDG with an improperly developed, small eye phenotype.

Evolutionary rate covariation is pervasive between glycosylation pathways and points to potential disease modifiers.

Mutations in glycosylation pathways, such as N-linked glycosylation, O-linked glycosylation, and GPI anchor synthesis, lead to Congenital Disorders of Glycosylation (CDG). CDG typically present with seizures, hypotonia, and developmental delay but display large clinical variability with symptoms affecting every system in the body. This variability suggests modifier genes might influence the phenotypes.

Identification of as a genetic modifier of PIGA-CDG through pedigree analysis of a family with incomplete penetrance and functional testing in .

Loss of function mutations in the X-linked gene lead to PIGA-CDG, an ultra-rare congenital disorder of glycosylation (CDG), typically presenting with seizures, hypotonia, and neurodevelopmental delay. We identified two brothers (probands) with PIGA-CDG, presenting with epilepsy and mild developmental delay. Both probands carry , an ultra-rare variant predicted to be damaging.

Drosophila models of phosphatidylinositol glycan biosynthesis class A congenital disorder of glycosylation (PIGA-CDG) mirror patient phenotypes.

Mutations in the phosphatidylinositol glycan biosynthesis class A (PIGA) gene cause a rare, X-linked recessive congenital disorder of glycosylation. Phosphatidylinositol glycan biosynthesis class A congenital disorder of glycosylation (PIGA-CDG) is characterized by seizures, intellectual and developmental delay, and congenital malformations. The PIGA gene encodes an enzyme involved in the first step of glycosylphosphatidylinositol (GPI) anchor biosynthesis.

A Drosophila screen identifies a role for histone methylation in ER stress preconditioning.

Stress preconditioning occurs when transient, sublethal stress events impact an organism's ability to counter future stresses. Although preconditioning effects are often noted in the literature, very little is known about the underlying mechanisms. To model preconditioning, we exposed a panel of genetically diverse Drosophila melanogaster to a sublethal heat shock and measured how well the flies survived subsequent exposure to endoplasmic reticulum (ER) stress.

models of PIGA-CDG mirror patient phenotypes.

Mutations in the phosphatidylinositol glycan biosynthesis class A (PIGA) gene cause a rare, X-linked recessive congenital disorder of glycosylation (CDG). PIGA-CDG is characterized by seizures, intellectual and developmental delay, and congenital malformations. The gene encodes an enzyme involved in the first step of GPI anchor biosynthesis.

Characterizing genetic variation in the regulation of the ER stress response through computational and cis-eQTL analyses.

Misfolded proteins in the endoplasmic reticulum (ER) elicit the ER stress response, a large transcriptional response driven by 3 well-characterized transcription factors (TFs). This transcriptional response is variable across different genetic backgrounds. One mechanism in which genetic variation can lead to transcriptional variability in the ER stress response is through altered binding and activity of the 3 main TFs: XBP1, ATF6, and ATF4.

A screen identifies a role for histone methylation in ER stress preconditioning.

Stress preconditioning occurs when transient, sublethal stress events impact an organism's ability to counter future stresses. Although preconditioning effects are often noted in the literature, very little is known about the underlying mechanisms. To model preconditioning, we exposed a panel of genetically diverse to a sublethal heat shock and measured how well the flies survived subsequent exposure to endoplasmic reticulum (ER) stress.

DIS3 Variants are Associated With Primary Ovarian Insufficiency: Importance of Transcription/Translation in Oogenesis.

Context: A genetic etiology accounts for the majority of unexplained primary ovarian insufficiency (POI).

Objective: We hypothesized a genetic cause of POI for a sister pair with primary amenorrhea.

Design: The study was an observational study.

A genome-wide CRISPR screen identifies DPM1 as a modifier of DPAGT1 deficiency and ER stress.

Partial loss-of-function mutations in glycosylation pathways underlie a set of rare diseases called Congenital Disorders of Glycosylation (CDGs). In particular, DPAGT1-CDG is caused by mutations in the gene encoding the first step in N-glycosylation, DPAGT1, and this disorder currently lacks effective therapies. To identify potential therapeutic targets for DPAGT1-CDG, we performed CRISPR knockout screens in Drosophila cells for genes associated with better survival and glycoprotein levels under DPAGT1 inhibition.

An in vivo drug repurposing screen and transcriptional analyses reveals the serotonin pathway and GSK3 as major therapeutic targets for NGLY1 deficiency.

NGLY1 deficiency, a rare disease with no effective treatment, is caused by autosomal recessive, loss-of-function mutations in the N-glycanase 1 (NGLY1) gene and is characterized by global developmental delay, hypotonia, alacrima, and seizures. We used a Drosophila model of NGLY1 deficiency to conduct an in vivo, unbiased, small molecule, repurposing screen of FDA-approved drugs to identify therapeutic compounds. Seventeen molecules partially rescued lethality in a patient-specific NGLY1 deficiency model, including multiple serotonin and dopamine modulators.

The dynamic effect of genetic variation on the in vivo ER stress transcriptional response in different tissues.

The genetic regulation of gene expression varies greatly across tissue-type and individuals and can be strongly influenced by the environment. Many variants, under healthy control conditions, may be silent or even have the opposite effect under diseased stress conditions. This study uses an in vivo mouse model to investigate how the effect of genetic variation changes with cellular stress across different tissues.

Causal and Candidate Gene Variants in a Large Cohort of Women With Primary Ovarian Insufficiency.

Context: A genetic etiology likely accounts for the majority of unexplained primary ovarian insufficiency (POI).

Objective: We hypothesized that heterozygous rare variants and variants in enhanced categories are associated with POI.

Design: The study was an observational study.

A screen identifies NKCC1 as a modifier of NGLY1 deficiency.

N-Glycanase 1 (NGLY1) is a cytoplasmic deglycosylating enzyme. Loss-of-function mutations in the gene cause NGLY1 deficiency, which is characterized by developmental delay, seizures, and a lack of sweat and tears. To model the phenotypic variability observed among patients, we crossed a model of NGLY1 deficiency onto a panel of genetically diverse strains.

Decoupling of Apoptosis from Activation of the ER Stress Response by the Metallopeptidase .

Endoplasmic reticulum (ER) stress-induced apoptosis is a primary cause and modifier of degeneration in a number of genetic disorders. Understanding how genetic variation influences the ER stress response and subsequent activation of apoptosis could improve individualized therapies and predictions of outcomes for patients. In this study, we find that the uncharacterized, membrane-bound metallopeptidase in , which we rename as (), plays a role in modifying ER stress-induced apoptosis.

Insulin Potentiates JAK/STAT Signaling to Broadly Inhibit Flavivirus Replication in Insect Vectors.

The World Health Organization estimates that more than half of the world's population is at risk for vector-borne diseases, including arboviruses. Because many arboviruses are mosquito borne, investigation of the insect immune response will help identify targets to reduce the spread of arboviruses. Here, we use a genetic screening approach to identify an insulin-like receptor as a component of the immune response to arboviral infection.

Natural Genetic Variation Screen in Identifies Wnt Signaling, Mitochondrial Metabolism, and Redox Homeostasis Genes as Modifiers of Apoptosis.

Apoptosis is the primary cause of degeneration in a number of neuronal, muscular, and metabolic disorders. These diseases are subject to a great deal of phenotypic heterogeneity in patient populations, primarily due to differences in genetic variation between individuals. This creates a barrier to effective diagnosis and treatment.

Baldspot/ELOVL6 is a conserved modifier of disease and the ER stress response.

Endoplasmic reticulum (ER) stress is an important modifier of human disease. Genetic variation in response genes is linked to inter-individual differences in the ER stress response. However, the mechanisms and pathways by which genetic modifiers are acting on the ER stress response remain unclear.

Genetic Modifiers of Neurodegeneration in a Model of Parkinson's Disease.

Disease phenotypes can be highly variable among individuals with the same pathogenic mutation. There is increasing evidence that background genetic variation is a strong driver of disease variability in addition to the influence of environment. To understand the genotype-phenotype relationship that determines the expressivity of a pathogenic mutation, a large number of backgrounds must be studied.

Transcriptome and functional analysis in a Drosophila model of NGLY1 deficiency provides insight into therapeutic approaches.

Autosomal recessive loss-of-function mutations in N-glycanase 1 (NGLY1) cause NGLY1 deficiency, the only known human disease of deglycosylation. Patients present with developmental delay, movement disorder, seizures, liver dysfunction and alacrima. NGLY1 is a conserved cytoplasmic component of the Endoplasmic Reticulum Associated Degradation (ERAD) pathway.

Roles of Female and Male Genotype in Post-Mating Responses in Drosophila melanogaster.

Mating induces a multitude of changes in female behavior, physiology, and gene expression. Interactions between female and male genotype lead to variation in post-mating phenotypes and reproductive success. So far, few female molecules responsible for these interactions have been identified.

Etiology of Human Genetic Disease on the Fly.

The model organism Drosophila melanogaster has been at the forefront of genetic studies since before the discovery of DNA. Although human disease modeling in flies may still be rather novel, recent advances in genetic tool design and genome sequencing now confer huge advantages in the fly system when modeling human disease. In this review, we focus on new genomic tools for human gene variant analysis; new uses for the Drosophila Genetic Reference Panel (DGRP) in detection of background alleles that influence a phenotype; and several examples of how multigenic conditions, both complex disorders and duplication and/or deletion syndromes, can be effectively studied in the fly model system.

Candidate genetic modifiers of retinitis pigmentosa identified by exploiting natural variation in Drosophila.

Individuals carrying the same pathogenic mutation can present with a broad range of disease outcomes. While some of this variation arises from environmental factors, it is increasingly recognized that the background genetic variation of each individual can have a profound effect on the expressivity of a pathogenic mutation. In order to understand this background effect on disease-causing mutations, studies need to be performed across a wide range of backgrounds.

Bringing genetic background into focus.

Researchers should embrace differences in genetic background to build richer disease models that more accurately reflect the level of variation in the human population, posits Clement Chow.

Induction of excessive endoplasmic reticulum stress in the Drosophila male accessory gland results in infertility.

Endoplasmic reticulum (ER) stress occurs when misfolded proteins accumulate in the lumen of the ER. A cell responds to ER stress with the unfolded protein response (UPR), a complex program of transcriptional and translational changes aimed at clearing misfolded proteins. Secretory tissues and cells are particularly well adapted to respond to ER stress because their function requires high protein production and secretory load.