Thyroid cancer is the most common endocrine malignancy and nonmedullary thyroid carcinoma (NMTC) represents 90% of all cases. NMTC risk in first-degree relatives of affected cases is elevated fivefold to ninefold. Familial NMTC (FNMTC) accounts for about 3-7% of all thyroid tumors and is a more aggressive clinical entity than its sporadic counterparts. Linkage analysis on high-risk families performed a decade ago mapped several susceptibility loci, but did not lead to the identification of high-penetrance causal germline mutations. More recently, a genome-wide association study (GWAS) identified common single nucleotide polymorphisms (SNPs) affecting the risk of sporadic NMTC. We sought to verify if the newly identified genetic risk factors for NMTC are relevant for FNMTC as well. We genotyped 23 SNPs at 11 candidate loci in 672 subjects belonging to 133 pedigrees with at least two NMTC cases. Statistical analysis was performed using family-based association tests, modified quasi-likelihood score and logistic-normal models. SNPs at 9q22.33 near FOXE1 showed convincing evidence of association with NMTC risk in these high-risk families. The other tested loci resulted negative. These findings confirm the importance of the SNPs identified by recent GWAS on sporadic NMTC on FNMTC as well. However, the proposed FOXE1 causal variants do not show the strongest association signal. Moreover, mutation screening of the FOXE1 coding sequence in the FNMTC cases did not identify rarer causal variants, suggesting that other yet unidentified variants at this locus are involved in FNMTC etiology.Nonmedullary thyroid carcinoma (NMTC) is a welldifferentiated thyroid cancer of follicular cell origin [either papillary thyroid carcinoma (PTC) or follicular thyroid carcinoma (FTC)], which represents the most common endocrine malignancy. The annual incidence rate throughout the world ranges from 0.5 to 10 cases per 100,000 people and there is a twofold to fourfold higher incidence of new thyroid cancer cases in women than in men.1 In Europe, thyroid cancer affects 47,240 individuals annually, with an estimated mortality rate of 6,366 patients each year.2 The incidence of thyroid cancer is increasing, with one of the fastest increasing rates among common cancers. Improvement in cancer diagnosis can partly explain the phenomenon. However, early diagnosis alone is unlikely to account for this increase, and environmental factors must also play a role. The major known environmental risk factor for PTC, which accounts for about 80% of all thyroid cancers, 1 is prior exposure to radiation, with a dose-dependent effect on cancer risk. Other risk factors for PTC include iodine deficiency and excess, previous history of benign thyroid disease, such as nodules and autoimmune thyroid disease, as well as a family history. Indeed, epidemiological studies have shown that the risk of thyroid cancer has a higher familial relative risk than any

Whole-genome sequencing methods in familial cancer are useful to unravel rare clinically important cancer predisposing variants. Here, we present improvements in our pedigree-based familial cancer variant prioritization pipeline referred as FCVPPv2, including 12 tools for evaluating deleteriousness and 5 intolerance scores for missense variants. This pipeline is also capable of assessing non-coding regions by combining FANTOM5 data with sets of tools like Bedtools, ChromHMM, Miranda, SNPnexus and Targetscan. We tested this pipeline in a family with history of a papillary thyroid cancer. Only one variant causing an amino acid change G573R (dbSNP ID rs145736623, NM_019609.4:exon11:c.G1717A:p.G573R) in the carboxypeptidase gene CPXM1 survived our pipeline. This variant is located in a highly conserved region across vertebrates in the peptidase_M14 domain (Pfam ID PF00246). The CPXM1 gene may be involved in adipogenesis and extracellular matrix remodelling and it has been suggested to be a tumour suppressor in breast cancer. However, the presence of the variant in the ExAC database suggests it to be a rare polymorphism or a low-penetrance risk allele. Overall, our pipeline is a comprehensive approach for prediction of predisposing variants for high-risk cancer families, for which a functional characterization is a crucial step to confirm their role in cancer predisposition.

Intellectual disability (ID) and autism spectrum disorders (ASDs) are complex neuropsychiatric conditions, with overlapping clinical boundaries in many patients. We identified a novel intragenic deletion of maternal origin in two siblings with mild ID and epilepsy in the CADPS2 gene, encoding for a synaptic protein involved in neurotrophin release and interaction with dopamine receptor type 2 (D2DR). Mutation screening of 223 additional patients (187 with ASD and 36 with ID) identified a missense change of maternal origin disrupting CADPS2/D2DR interaction. CADPS2 allelic expression was tested in blood and different adult human brain regions, revealing that the gene was monoallelically expressed in blood and amygdala, and the expressed allele was the one of maternal origin. Cadps2 gene expression performed in mice at different developmental stages was biallelic in the postnatal and adult stages; however, a monoallelic (maternal) expression was detected in the embryonal stage, suggesting that CADPS2 is subjected to tissue- and temporal-specific regulation in human and mice. We suggest that CADPS2 variants may contribute to ID/ASD development, possibly through a parent-of-origin effect.

Familial aggregation is a significant risk factor for the development of thyroid cancer and familial non-medullary thyroid cancer (FNMTC) accounts for 5-7% of all NMTC. Whole exome sequencing analysis in the family affected by FNMTC with oncocytic features where our group previously identified a predisposing locus on chromosome 19p13.2, revealed a novel heterozygous mutation (c.400G > A, NM_012335; p.Gly134Ser) in exon 5 of MYO1F, mapping to the linkage locus. In the thyroid FRTL-5 cell model stably expressing the mutant MYO1F p.Gly134Ser protein, we observed an altered mitochondrial network, with increased mitochondrial mass and a significant increase in both intracellular and extracellular reactive oxygen species, compared to cells expressing the wild-type (wt) protein or carrying the empty vector. The mutation conferred a significant advantage in colony formation, invasion and anchorage-independent growth. These data were corroborated by in vivo studies in zebrafish, since we demonstrated that the mutant MYO1F p.Gly134Ser, when overexpressed, can induce proliferation in whole vertebrate embryos, compared to the wt one. MYO1F screening in additional 192 FNMTC families identified another variant in exon 7, which leads to exon skipping, and is predicted to alter the ATP-binding domain in MYO1F. Our study identified for the first time a role for MYO1F in NMTC.

Abnormal gut motility is a feature of several mitochondrial encephalomyopathies, and mutations in genes such as TYMP and POLG, have been linked to these rare diseases. The human genome encodes three DNA ligases, of which only one, ligase III (LIG3), has a mitochondrial splice variant and is crucial for mitochondrial health. We investigated the effect of reduced LIG3 activity and resulting mitochondrial dysfunction in seven patients from three independent families, who showed the common occurrence of gut dysmotility and neurological manifestations reminiscent of mitochondrial neurogastrointestinal encephalomyopathy. DNA from these patients was subjected to whole exome sequencing. In all patients, compound heterozygous variants in a new disease gene, LIG3, were identified. All variants were predicted to have a damaging effect on the protein. The LIG3 gene encodes the only mitochondrial DNA (mtDNA) ligase and therefore plays a pivotal role in mtDNA repair and replication. In vitro assays in patient-derived cells showed a decrease in LIG3 protein levels and ligase activity. We demonstrated that the LIG3 gene defects affect mtDNA maintenance, leading to mtDNA depletion without the accumulation of multiple deletions as observed in other mitochondrial disorders. This mitochondrial dysfunction is likely to cause the phenotypes observed in these patients. The most prominent and consistent clinical signs were severe gut dysmotility and neurological abnormalities, including leukoencephalopathy, epilepsy, migraine, stroke-like episodes, and neurogenic bladder. A decrease in the number of myenteric neurons, and increased fibrosis and elastin levels were the most prominent changes in the gut. Cytochrome c oxidase (COX) deficient fibres in skeletal muscle were also observed. Disruption of lig3 in zebrafish reproduced the brain alterations and impaired gut transit in vivo. In conclusion, we identified variants in the LIG3 gene that result in a mitochondrial disease characterized by predominant gut dysmotility, encephalopathy, and neuromuscular abnormalities. Bonora et al. identify a new mitochondrial recessive disorder caused by biallelic variants in the LIG3 gene encoding DNA ligase III, which is responsible for mitochondrial DNA repair. Clinical signs include gut dysmotility and neurological features such as leucoencephalopathy, epilepsy and stroke-like episodes.

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Loss‐of‐function mutations in the SPART gene cause Troyer syndrome, a recessive form of spastic paraplegia resulting in muscle weakness, short stature, and cognitive defects. SPART encodes for Spartin, a protein linked to endosomal trafficking and mitochondrial membrane potential maintenance. Here, we identified with whole exorne sequencing (WES) a novel frameshift mutation in the SPART gene in 2 brothers presenting an uncharacterized developmental delay and short stature. Functional characterization in an SH‐SY5Y cell model shows that this mutation is associated with increased neurite outgrowth. These cells also show a marked decrease in mitochondrial complex I (NADH dehydrogenase) activity, coupled to decreased ATP synthesis and defective mitochondrial membrane potential. The cells also presented an increase in reactive oxygen species, extracellular pyruvate, and NADH levels, consistent with impaired complex I activity. In concordance with a severe mitochondrial failure, Spartin loss also led to an altered intracellular Ca2+ homeostasis that was restored after transient expression of wild‐type Spartin. Our data provide for the first time a thorough assessment of Spartin loss effects, including impaired complex I activity coupled to increased extracellular pyruvate. In summary, through a WES study we assign a diagnosis of Troyer syndrome to otherwise undiagnosed patients, and by functional characterization we show that the novel mutation in SPART leads to a profound bioenergetic imbalance.—Diquigiovanni, C., Bergamini, C., Diaz, R., Liparulo, I., Bianco, F., Masin, L., Baldassarro, V. A., Rizzardi, N., Tranchina, A., Buscherini, F., Wischmeijer, A., Pippucci, T., Scarano, E., Cordelli, D. M., Fato, R., Seri, M., Paracchini, S., Bonora, E. A novel mutation in SPART gene causes a severe neurodevelopmental delay due to mitochondrial dysfunction with complex I impairments and altered pyruvate metabolism. FASEB J. 33, 11284–11302 (2019). http://www.fasebj.org

Familial inheritance in non-medullary thyroid cancer (NMTC) is an area that has yet to be adequately explored. Despite evidence suggesting strong familial clustering of non-syndromic NMTC, known variants still account for a very small percentage of the genetic burden. In a recent whole genome sequencing (WGS) study of five families with several NMTCs, we shortlisted promising variants with the help of our in-house developed Familial Cancer Variant Prioritization Pipeline (FCVPPv2). Here, we report potentially disease-causing variants in checkpoint kinase 2 (CHEK2), Ewing sarcoma breakpoint region 1 (EWSR1) and T-lymphoma invasion and metastasis-inducing protein 1 (TIAM1) in one family. Performing WGS on three cases, one probable case and one healthy individual in a family with familial NMTC left us with 112254 variants with a minor allele frequency of less than 0.1%, which was reduced by pedigree-based filtering to 6368. Application of the pipeline led to the prioritization of seven coding and nine non-coding variants from this family. The variant identified in CHEK2, a known tumor suppressor gene involved in DNA damage-induced DNA repair, cell cycle arrest, and apoptosis, has been previously identified as a germline variant in breast and prostate cancer and has been functionally validated by Roeb et al. in a yeast-based assay to have an intermediate effect on protein function. We thus hypothesized that this family may harbor additional disease-causing variants in other functionally related genes. We evaluated two further variants in EWSR1 and TIAM1 with promising in silico results and reported interaction in the DNA-damage repair pathway. Hence, we propose a polygenic mode of inheritance in this family. As familial NMTC is considered to be more aggressive than its sporadic counterpart, it is important to identify such susceptibility genes and their associated pathways. In this way, the advancement of personalized medicine in NMTC patients can be fostered. We also wish to reopen the discussion on monogenic vs polygenic inheritance in NMTC and instigate further development in this area of research.