Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a severe developmental disorder spectrum.

PURPOSE: FLVCR1 encodes a solute carrier (SLC) protein implicated in heme, choline, and ethanolamine transport. While Flvcr1-/- mice exhibit skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia (DBA), biallelic FLVCR1 variants in humans have previously only been linked to childhood or adult-onset ataxia, sensory neuropathy, and retinitis pigmentosa. METHODS: We identified individuals with undiagnosed neurodevelopmental disorders and biallelic FLVCR1 variants through international data sharing and characterized the functional consequences of their FLVCR1 variants. RESULTS: We ascertained 30 patients from 23 unrelated families with biallelic FLVCR1 variants and characterized a novel FLVCR1-related phenotype: severe developmental disorders with profound developmental delay, microcephaly (Z-score -2.5 to -10.5), brain malformations, epilepsy, spasticity, and premature death. Brain malformations ranged from mild brain volume reduction to hydranencephaly. Severely affected patients share traits including macrocytic anemia and skeletal malformations with Flvcr1-/- mice and DBA. FLVCR1 variants significantly reduce choline and ethanolamine transport and/or disrupt mRNA splicing. CONCLUSION: These data demonstrate a broad FLVCR1-related phenotypic spectrum ranging from severe multiorgan developmental disorders resembling DBA to adult-onset neurodegeneration. Our study expands our understanding of Mendelian choline and ethanolamine disorders and illustrates the importance of anticipating a wide phenotypic spectrum for known disease genes and incorporating model organism data into genome analysis to maximize genetic testing yield.

Telehealth genetic services during the COVID-19 Pandemic: Implementation and patient experiences across multiple specialties in Nebraska.

The COVID-19 pandemic has altered the delivery of genetics services. In response to the pandemic, our genetics department offered telehealth visits to all outpatients, regardless of their physical proximity to Omaha, Nebraska. Traditionally, our department did not offer telehealth visits to patient's homes or to patients who lived in close proximity to a genetics clinic. Therefore, we designed a survey to gain insight into the patient experience with remote genetic counseling appointments during the pandemic. Any patient referred to see a genetics provider in pediatrics, prenatal, adult, or cancer between March 16, 2020 and October 28, 2020 was eligible for the study. The survey included both quantitative and qualitative measures to assess patient demographics, patient experience, stressors during the COVID-19 pandemic, and anxiety and depression. We hypothesized that patients would report they received quality care by telehealth despite the presence of COVID-19-related stressors or anxiety/depression. From the 143 survey participants, 80% had their first telehealth appointment during the pandemic. The vast majority (96%) reported that they felt like they received quality care by telehealth. Additionally, more than 93% of participants strongly or somewhat agreed that their genetic providers were attentive to their emotional needs, medical needs, and privacy. Since March 2020, participants reported experiencing several COVID-19-related stressors including fear of illness (86%), feelings of isolation (45%), and safety concerns (33%). Relatively low levels of depressive and anxiety symptoms were recorded using the HADS questionnaire. Despite the prevalence of COVID-19 stressors, depression, and/or anxiety, our participants felt they received quality care via telehealth. In fact, 51% agree that they prefer to receive future genetics services virtually. These results suggest the value of telehealth as an alternative service delivery model, even for local patients, and should be offered for future appointments, beyond the COVID-19 pandemic.

Biallelic variation in the choline and ethanolamine transporter FLVCR1 underlies a pleiotropic disease spectrum from adult neurodegeneration to severe developmental disorders.

FLVCR1 encodes Feline leukemia virus subgroup C receptor 1 (FLVCR1), a solute carrier (SLC) transporter within the Major Facilitator Superfamily. FLVCR1 is a widely expressed transmembrane protein with plasma membrane and mitochondrial isoforms implicated in heme, choline, and ethanolamine transport. While Flvcr1 knockout mice die in utero with skeletal malformations and defective erythropoiesis reminiscent of Diamond-Blackfan anemia, rare biallelic pathogenic FLVCR1 variants are linked to childhood or adult-onset neurodegeneration of the retina, spinal cord, and peripheral nervous system. We ascertained from research and clinical exome sequencing 27 individuals from 20 unrelated families with biallelic ultra-rare missense and predicted loss-of-function (pLoF) FLVCR1 variant alleles. We characterize an expansive FLVCR1 phenotypic spectrum ranging from adult-onset retinitis pigmentosa to severe developmental disorders with microcephaly, reduced brain volume, epilepsy, spasticity, and premature death. The most severely affected individuals, including three individuals with homozygous pLoF variants, share traits with Flvcr1 knockout mice and Diamond-Blackfan anemia including macrocytic anemia and congenital skeletal malformations. Pathogenic FLVCR1 missense variants primarily lie within transmembrane domains and reduce choline and ethanolamine transport activity compared with wild-type FLVCR1 with minimal impact on FLVCR1 stability or subcellular localization. Several variants disrupt splicing in a mini-gene assay which may contribute to genotype-phenotype correlations. Taken together, these data support an allele-specific gene dosage model in which phenotypic severity reflects residual FLVCR1 activity. This study expands our understanding of Mendelian disorders of choline and ethanolamine transport and demonstrates the importance of choline and ethanolamine in neurodevelopment and neuronal homeostasis.