A point mutation in PTPRC is associated with the development of multiple sclerosis

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. It is widely accepted that a dysregulated immune response against brain resident antigens is central to its yet unknown pathogenesis. Although there is evidence that the development of MS has a genetic component, specific genetic factors are largely unknown. Here we investigated the role of a point mutation in the gene (PTPRC) encoding protein-tyrosine phosphatase, receptor-type C (also known as CD45) in the heterozygous state in the development of MS. The nucleotide transition in exon 4 of the gene locus interferes with mRNA splicing and results in altered expression of CD45 isoforms on immune cells. In three of four independent case-control studies, we demonstrated an association of the mutation with MS. We found the PTPRC mutation to be linked to and associated with the disease in three MS nuclear families. In one additional family, we found the same variant CD45 phenotype, with an as-yet-unknown origin, among the members affected with MS. Our findings suggest an association of the mutation in PTPRC with the development of MS in some families.     

A mutation in SLC11A3 is associated with autosomal dominant hemochromatosis.

Hereditary hemochromatosis (HH) is a very common disorder characterized by iron overload and multi-organ damage. Several genes involved in iron metabolism have been implicated in the pathology of HH (refs. 1-4). We report that a mutation in the gene encoding Solute Carrier family 11, member A3 (SLC11A3), also known as ferroportin, is associated with autosomal dominant hemochromatosis.     

Mutations in RAI1 associated with Smith-Magenis syndrome

Smith-Magenis syndrome (SMS) is a mental retardation syndrome associated with deletions involving chromosome 17p11.2. Persons with SMS have characteristic behavioral abnormalities, including self-injurious behaviors and sleep disturbance, and distinct craniofacial and skeletal anomalies. We identified dominant frameshift mutations leading to protein truncation in RAI1 in three individuals who have phenotypic features consistent with SMS but do not have 17p11.2 deletions detectable by standard fluorescence in situ hybridization techniques.     

A rare variant in MYH6 is associated with high risk of sick sinus syndrome

Through complementary application of SNP genotyping, whole-genome sequencing and imputation in 38,384 Icelanders, we have discovered a previously unidentified sick sinus syndrome susceptibility gene, MYH6, encoding the alpha heavy chain subunit of cardiac myosin. A missense variant in this gene, c.2161C>T, results in the conceptual amino acid substitution p.Arg721Trp, has an allelic frequency of 0.38% in Icelanders and associates with sick sinus syndrome with an odds ratio = 12.53 and P = 1.5 × 10?2?. We show that the lifetime risk of being diagnosed with sick sinus syndrome is around 6% for non-carriers of c.2161C>T but is approximately 50% for carriers of the c.2161C>T variant.     

A single EFEMP1 mutation associated with both Malattia Leventinese and Doyne honeycomb retinal dystrophy.

Malattia Leventinese (ML) and Doyne honeycomb retinal dystrophy (DHRD) refer to two autosomal dominant diseases characterized by yellow-white deposits known as drusen that accumulate beneath the retinal pigment epithelium (RPE). Both loci were mapped to chromosome 2p16-21 (refs 5,6) and this genetic interval has been subsequently narrowed. The importance of these diseases is due in large part to their close phenotypic similarity to age-related macular degeneration (AMD), a disorder with a strong genetic component that accounts for approximately 50% of registered blindness in the Western world. Just as in ML and DHRD, the early hallmark of AMD is the presence of drusen. Here we use a combination of positional and candidate gene methods to identify a single non-conservative mutation (Arg345Trp) in the gene EFEMP1 (for EGF-containing fibrillin-like extracellular matrix protein 1) in all families studied. This change was not present in 477 control individuals or in 494 patients with age-related macular degeneration. Identification of this mutation may aid in the development of an animal model for drusen, as well as in the identification of other genes involved in human macular degeneration.     

Common variation in GPC5 is associated with acquired nephrotic syndrome

Severe proteinuria is a defining factor of nephrotic syndrome irrespective of the etiology. Investigation of congenital nephrotic syndrome has shown that dysfunction of glomerular epithelial cells (podocytes) plays a crucial role in this disease. Acquired nephrotic syndrome is also assumed to be associated with podocyte injury. Here we identify an association between variants in GPC5, encoding glypican-5, and acquired nephrotic syndrome through a genome-wide association study and replication analysis (P value under a recessive model (P(rec)) = 6.0 × 10(-11), odds ratio = 2.54). We show that GPC5 is expressed in podocytes and that the risk genotype is associated with higher expression. We further show that podocyte-specific knockdown and systemic short interfering RNA injection confers resistance to podocyte injury in mouse models of nephrosis. This study identifies GPC5 as a new susceptibility gene for nephrotic syndrome and implicates GPC5 as a promising therapeutic target for reducing podocyte vulnerability in glomerular disease.     

A common variant at the TERT-CLPTM1L locus is associated with estrogen receptor-negative breast cancer

Estrogen receptor (ER)-negative breast cancer shows a higher incidence in women of African ancestry compared to women of European ancestry. In search of common risk alleles for ER-negative breast cancer, we combined genome-wide association study (GWAS) data from women of African ancestry (1,004 ER-negative cases and 2,745 controls) and European ancestry (1,718 ER-negative cases and 3,670 controls), with replication testing conducted in an additional 2,292 ER-negative cases and 16,901 controls of European ancestry. We identified a common risk variant for ER-negative breast cancer at the TERT-CLPTM1L locus on chromosome 5p15 (rs10069690: per-allele odds ratio (OR) = 1.18 per allele, P = 1.0 × 10(-10)). The variant was also significantly associated with triple-negative (ER-negative, progesterone receptor (PR)-negative and human epidermal growth factor-2 (HER2)-negative) breast cancer (OR = 1.25, P = 1.1 × 10(-9)), particularly in younger women (<50 years of age) (OR = 1.48, P = 1.9 × 10(-9)). Our results identify a genetic locus associated with estrogen receptor negative breast cancer subtypes in multiple populations.     

Mutations in RAB27A cause Griscelli syndrome associated with haemophagocytic syndrome

Griscelli syndrome (GS, MIM 214450), a rare, autosomal recessive disorder, results in pigmentary dilution of the skin and the hair, the presence of large clumps of pigment in hair shafts and an accumulation of melanosomes in melanocytes. Most patients also develop an uncontrolled T-lymphocyte and macrophage activation syndrome (known as haemophagocytic syndrome, HS), leading to death in the absence of bone-marrow transplantation. In contrast, early in life some GS patients show a severe neurological impairment without apparent immune abnormalities. We previously mapped the GS locus to chromosome 15q21 and found a mutation in a gene (MYO5A) encoding a molecular motor in two patients. Further linkage analysis suggested a second gene associated with GS was in the same chromosomal region. Homozygosity mapping in additional families narrowed the candidate region to a 3.1-cM interval between D15S1003 and D15S962. We detected mutations in RAB27A, which lies within this interval, in 16 patients with GS. Unlike MYO5A, the GTP-binding protein RAB27A appears to be involved in the control of the immune system, as all patients with RAB27A mutations, but none with the MYO5A mutation, developed HS. In addition, RAB27A-deficient T cells exhibited reduced cytotoxicity and cytolytic granule exocytosis, whereas MYO5A-defective T cells did not. RAB27A appears to be a key effector of cytotoxic granule exocytosis, a pathway essential for immune homeostasis.     

A mutation in adenylosuccinate lyase associated with mental retardation and autistic features.

We have examined the molecular basis of three cases of severe mental retardation with autistic features in one family. A point mutation in a purine nucleotide biosynthetic enzyme, adenylosuccinate lyase (ASL), segregates with the disorder. The affected children are homozygous for the point mutation while the parents and all four unaffected children are heterozygous. The point mutation is absent in control subjects. The point mutation results in a Ser413Pro substitution which leads to structural instability of the recombinant mutant enzyme, and this instability lowers ASL levels in lymphocytes. These observations suggest that the instability of ASL underlies the severe developmental disorder in the affected children, and that mutations in the ASL gene may result in other cases of mental retardation and autistic features.     

MYCN haploinsufficiency is associated with reduced brain size and intestinal atresias in Feingold syndrome

Feingold syndrome is characterized by variable combinations of esophageal and duodenal atresias, microcephaly, learning disability, syndactyly and cardiac defect. We show here that heterozygous mutations in the gene MYCN are present in Feingold syndrome. All mutations are predicted to disrupt both the full-length protein and a new shortened MYCN isoform, suggesting that multiple aspects of early embryogenesis and postnatal brain growth in humans are tightly regulated by MYCN dosage.