First female with Allan-Herndon-Dudley syndrome and partial deletion of X-inactivation center.

Allan-Herndon-Dudley is an X-linked recessive syndrome caused by pathogenic variants in the SLC16A2 gene. Clinical manifestations are a consequence of impaired thyroid metabolism and aberrant transport of thyroid hormones to the brain. Carrier females are generally asymptomatic and may show subtle symptoms of the disease. We describe a female with a complete Allan-Herndon-Dudley phenotype, carrying a de novo 543-kb deletion of the X chromosome. The deletion encompasses exon 1 of the SLC16A2 gene and JPX and FTX genes; it is known that the latter two genes participate in the X-inactivation process upregulating XIST gene expression. Subsequent studies in the patient demonstrated the preferential expression of the X chromosome with the JPX and FTX deletion.

SpadaHC: a database to improve the classification of variants in hereditary cancer genes in the Spanish population.

Accurate classification of genetic variants is crucial for clinical decision-making in hereditary cancer. In Spain, genetic diagnostic laboratories have traditionally approached this task independently due to the lack of a dedicated resource. Here we present SpadaHC, a web-based database for sharing variants in hereditary cancer genes in the Spanish population. SpadaHC is implemented using a three-tier architecture consisting of a relational database, a web tool and a bioinformatics pipeline. Contributing laboratories can share variant classifications and variants from individuals in Variant Calling Format (VCF) format. The platform supports open and restricted access, flexible dataset submissions, automatic pseudo-anonymization, VCF quality control, variant normalization and liftover between genome builds. Users can flexibly explore and search data, receive automatic discrepancy notifications and access SpadaHC population frequencies based on many criteria. In February 2024, SpadaHC included 18 laboratory members, storing 1.17 million variants from 4306 patients and 16 343 laboratory classifications. In the first analysis of the shared data, we identified 84 genetic variants with clinically relevant discrepancies in their classifications and addressed them through a three-phase resolution strategy. This work highlights the importance of data sharing to promote consistency in variant classifications among laboratories, so patients and family members can benefit from more accurate clinical management. Database URL: https://spadahc.ciberisciii.es/.

Fragile X-associated tremor/ataxia syndrome: Regional decrease of mitochondrial DNA copy number relates to clinical manifestations.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that appears in at least one-third of adult carriers of a premutation (55-200 CGG repeats) in the fragile X mental retardation 1 (FMR1) gene. Several studies have shown that mitochondrial dysfunction may play a central role in aging and also in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease as well as in FXTAS. It has been recently proposed that mtDNA copy number, measured by the number of mitochondrial genomes per nuclear genome (diploid), could be a useful biomarker of mitochondrial dysfunction. In order to elucidate the role of mtDNA variation in the pathogenesis of FXTAS, mtDNA copy number was quantified by digital droplet Polymerase chain reaction. In human brain samples, mtDNA levels were measured in the cerebellar vermis, dentate nucleus, parietal and temporal cortex, thalamus, caudate nucleus and hippocampus from a female FXTAS patient, a FMR1 premutation male carrier without FXTAS and from three male controls. The mtDNA copy number was further analyzed using this technology in dermal fibroblasts primary cultures derived from three FXTAS patients and three controls as well as in cortex and cerebellum of a CGG knock in FXTAS mice model. Finally, qPCR was carried out in human blood samples. Results indicate reduced mtDNA copy number in the specific brain region associated with disease progression in FXTAS patients, providing new insights into the role of mitochondrial dysfunction in the pathogenesis of FXTAS.