Simon T. Cliffe

SLC29A3 gene is mutated in pigmented hypertrichosis with insulin-dependent diabetes mellitus syndrome and interacts with the insulin signaling pathway

Pigmented hypertrichotic dermatosis with insulin-dependent diabetes (PHID) syndrome is a recently described autosomal recessive disorder associated with predominantly antibody negative, insulin-dependent diabetes mellitus. In order to identify the genetic basis of PHID and study its relationship with glucose metabolism, we performed homozygosity mapping in five unrelated families followed by candidate gene sequencing. Five loss-of-function mutations were identified in the SLC29A3 gene which encodes a member of a highly conserved protein family that transports nucleosides, nucleobases and nucleoside analogue drugs, hENT3. We show that PHID is allelic with a related syndrome without diabetes mellitus, H syndrome. The interaction of SLC29A3 with insulin signaling pathways was then studied using an established model in Drosophila melanogaster. Ubiquitous knockdown of the Drosophila ortholog of hENT3, dENT1 is lethal under stringent conditions; whereas milder knockdown induced scutellar bristle phenotypes similar to those previously reported in the knockdown of the Drosophila ortholog of the Islet gene. A cellular growth assay showed a reduction of cell size/number which could be rescued or enhanced by manipulation of the Drosophila insulin receptor and its downstream signaling effectors, dPI3K and dAkt. In summary, inactivating mutations in SLC29A3 cause a syndromic form of insulin-dependent diabetes in humans and in Drosophila profoundly affect cell size/number through interactions with the insulin signaling pathway. These data suggest that further investigation of the role of SLC29A3 in glucose metabolism is a priority for diabetes research.

Mutations in the gene encoding the PML nuclear body protein Sp110 are associated with immunodeficiency and hepatic veno-occlusive disease

We describe mutations in the PML nuclear body protein Sp110 in the syndrome veno-occlusive disease with immunodeficiency, an autosomal recessive disorder of severe hypogammaglobulinemia, combined T and B cell immunodeficiency, absent lymph node germinal centers, absent tissue plasma cells and hepatic veno-occlusive disease. This is the first report of the involvement of a nuclear body protein in a human primary immunodeficiency and of high-penetrance genetic mutations in hepatic veno-occlusive disease.

Expanding the clinical spectrum of SLC29A3 gene defects

H syndrome and pigmented hypertrichosis with insulin dependent diabetes (PHID) are allelic autosomal recessive syndromes reported in the last year to be caused by mutations in the SLC29A3 gene, which encodes the equilibrative nucleoside transporter hENT3. Herein, we report three new patients from a single family who present with phenotypes that associate features of both PHID and H syndrome. Genetic analysis of the SLC29A3 gene revealed that two affected sisters are compound heterozygotes for the previously reported mutations p.G427S and p.G437R, while their nephew was homozygous for the p.G437R mutation. In addition to this intra-familial genetic heterogeneity, these patients demonstrate considerable phenotypic variability. One sister had clinical features consistent with classical PHID phenotype, while her nephews features were in keeping with the diagnosis of H syndrome. The second sister displayed the most severe phenotype which combined diagnostic features from both syndromes. This patient also had features not described previously, including severe seronegative polyarthritis involving large and small joints, and hypogonadotropic hypogonadism. These manifestations may be additional characteristics of the growing clinical spectrum of SLC29A3 defects. This report emphasizes the complex genotype phenotype correlation in SLC29A3 disorders and suggests that other factors are relevant to disease manifestations and severity.

Hepatic veno-occlusive disease with immunodeficiency (VODI): first reported case in the U.S. and identification of a unique mutation in Sp110.

Familial hepatic veno-occlusive disease with immunodeficiency (VODI, OMIM: 235550), a rare form of severe combined immune deficiency, was first described in Australian Lebanese patients as being associated with homozygous mutations in SP110, a gene encoding a PML nuclear body-associated protein. We present the first case of confirmed VODI in the United States, and identify the first novel missense mutation in SP110. The 3-year-old daughter of Hispanic parents without known consanguinity presented at age 5 months with fever, hepatomegaly, and pancytopenia. Her brother died at age 3 months from hepatic failure of undetermined etiology. Initial T- and B-cell counts were low, but eventually normalized. Serum IgG and IgM levels were low for age. Lymphoproliferation to mitogens and allogenic B-cells was normal, but absent to tetanus and candida antigens. Serum antibody levels against pneumococcal, Hib and tetanus antigens were low. Liver biopsies at ages 5 and 9 months were consistent with hepatic veno-occlusive disease or hVOD (also known as sinusoidal obstruction syndrome or SOS) and broncho-alveolar lavage detected Pneumocystis jiroveci. The patient recovered from her acute disease and has been clinically stable on immunoglobulin replacement therapy and trimethoprim-sulfamethoxazole prophylaxis. T-Cell receptor excision circle (TREC) analysis suggests that VODI will not be detected by newborn screening for severe combined immunodeficiency that relies on this assay. DNA was obtained from the patient, 4 siblings, and both parents, and SP110 was sequenced. The first missense mutation, a homozygous deletion/insertion variation in exon 2 (NM_080424.2 (SP110):c.78_79delinsAT) was detected in the patient. This novel mutation segregated in the heterozygous state in other living unaffected family members. The mechanism by which this SP110 mutation associates with VODI is consistent with the normal length mutated SP110 protein being subject to enhanced proteosome degradation resulting in marked reductions in SP110 protein.

Breast cancer risk is not increased in individuals with TWIST1 mutation confirmed Saethre-Chotzen syndrome: an Australian multicenter study.

Saethre‐Chotzen syndrome (SCS) is a rare autosomal dominant syndrome involving craniosynostosis, craniofacial abnormalities, and syndactyly. A recent Scandinavian study reported an increased risk of breast cancer in individuals with a clinical diagnosis of SCS. Because of the potential importance of this finding, we organized a multicenter study enrolling people with TWIST1 mutation confirmed SCS to determine if an increased risk of cancer is present. This study did not identify any cases of breast or ovarian cancer in a cohort of equivalent power to that reported previously. These results provide clinical reassurance that at present there is no evidence for breast cancer screening above standard practice for individuals with SCS.