Sandra Hanks

PALB2, which encodes a BRCA2-interacting protein, is a breast cancer susceptibility gene

PALB2 interacts with BRCA2, and biallelic mutations in PALB2 (also known as FANCN), similar to biallelic BRCA2 mutations, cause Fanconi anemia. We identified monoallelic truncating PALB2 mutations in 10/923 individuals with familial breast cancer compared with 0/1,084 controls (P = 0.0004) and show that such mutations confer a 2.3-fold higher risk of breast cancer (95% confidence interval (c.i.) = 1.4–3.9, P = 0.0025). The results show that PALB2 is a breast cancer susceptibility gene and further demonstrate the close relationship of the Fanconi anemia–DNA repair pathway and breast cancer predisposition.

Biallelic mutations in PALB2 cause Fanconi anemia subtype FA-N and predispose to childhood cancer

PALB2 was recently identified as a nuclear binding partner of BRCA2. Biallelic BRCA2 mutations cause Fanconi anemia subtype FA-D1 and predispose to childhood malignancies. We identified pathogenic mutations in PALB2 (also known as FANCN) in seven families affected with Fanconi anemia and cancer in early childhood, demonstrating that biallelic PALB2 mutations cause a new subtype of Fanconi anemia, FA-N, and, similar to biallelic BRCA2 mutations, confer a high risk of childhood cancer.

Constitutional aneuploidy and cancer predisposition caused by biallelic mutations in BUB1B

Mosaic variegated aneuploidy is a rare recessive condition characterized by growth retardation, microcephaly, childhood cancer and constitutional mosaicism for chromosomal gains and losses. In five families with mosaic variegated aneuploidy, including two with embryonal rhabdomyosarcoma, we identified truncating and missense mutations of BUB1B, which encodes BUBR1, a key protein in the mitotic spindle checkpoint. These data are the first to relate germline mutations in a spindle checkpoint gene with a human disorder and strongly support a causal link between aneuploidy and cancer development.

NSD1 Mutations Are the Major Cause of Sotos Syndrome and Occur in Some Cases of Weaver Syndrome but Are Rare in Other Overgrowth Phenotypes

Sotos syndrome is a childhood overgrowth syndrome characterized by a distinctive facial appearance, height and head circumference >97th percentile, advanced bone age, and developmental delay. Weaver syndrome is characterized by the same criteria but has its own distinctive facial gestalt. Recently, a 2.2-Mb chromosome 5q35 microdeletion, encompassing NSD1, was reported as the major cause of Sotos syndrome, with intragenic NSD1 mutations identified in a minority of cases. We evaluated 75 patients with childhood overgrowth, for intragenic mutations and large deletions of NSD1. The series was phenotypically scored into four groups, prior to the molecular analyses: the phenotype in group 1 (n=37) was typical of Sotos syndrome; the phenotype in group 2 (n=13) was Sotos-like but with some atypical features; patients in group 3 (n=7) had Weaver syndrome, and patients in group 4 (n=18) had an overgrowth condition that was neither Sotos nor Weaver syndrome. We detected three deletions and 32 mutations (13 frameshift, 8 nonsense, 2 splice-site, and 9 missense) that are likely to impair NSD1 functions. The truncating mutations were spread throughout NSD1, but there was evidence of clustering of missense mutations in highly conserved functional domains between exons 13 and 23. There was a strong correlation between presence of an NSD1 alteration and clinical phenotype, in that 28 of 37 (76%) patients in group 1 had NSD1 mutations or deletions, whereas none of the patients in group 4 had abnormalities of NSD1. Three patients with Weaver syndrome had NSD1 mutations, all between amino acids 2142 and 2184. We conclude that intragenic mutations of NSD1 are the major cause of Sotos syndrome and account for some Weaver syndrome cases but rarely occur in other childhood overgrowth phenotypes.

DICER1 syndrome: clarifying the diagnosis, clinical features and management implications of a pleiotropic tumour predisposition syndrome

Background Constitutional DICER1 mutations were recently reported to cause familial pleuropulmonary blastoma (PPB). Aim To investigate the contribution and phenotypic spectrum of constitutional and somatic DICER1 mutations to cancer. Methods and results The authors sequenced DICER1 in constitutional DNA from 823 unrelated patients with a variety of tumours and in 781 cancer cell lines. Constitutional DICER1 mutations were identified in 19 families including 11/14 with PPB, 2/3 with cystic nephroma, 4/7 with ovarian Sertoli–Leydig-type tumours, 1/243 with Wilms tumour (this patient also had a Sertoli–Leydig tumour), 1/1 with intraocular medulloepithelioma (this patient also had PPB), 1/86 with medulloblastoma/infratentorial primitive neuroectodermal tumour, and 1/172 with germ cell tumour. The inheritance was investigated in 17 families. DICER1 mutations were identified in 25 relatives: 17 were unaffected, one mother had ovarian Sertoli–Leydig tumour, one half-sibling had cystic nephroma, and six relatives had non-toxic thyroid cysts/goitre. Analysis of eight tumours from DICER1 mutation-positive patients showed universal retention of the wild-type allele. DICER1 truncating mutations were identified in 4/781 cancer cell lines; all were in microsatellite unstable lines and therefore unlikely to be driver mutations. Conclusion Constitutional DICER1 haploinsufficiency predisposes to a broad range of tumours, making a substantial contribution to PPB, cystic nephroma and ovarian Sertoli–Leydig tumours, but a smaller contribution to other tumours. Most mutation carriers are unaffected, indicating that tumour risk is modest. The authors define the clinical contexts in which DICER1 mutation testing should be considered, the associated tumour risks, and the implications for at-risk individuals. They have termed this condition ‘DICER1 syndrome’. Accession numbers The cDNA Genbank accession number for the DICER1 sequence reported in this paper is NM_030621.2.

Mutations in the Gene Encoding Capillary Morphogenesis Protein 2 Cause Juvenile Hyaline Fibromatosis and Infantile Systemic Hyalinosis

Juvenile hyaline fibromatosis (JHF) and infantile systemic hyalinosis (ISH) are autosomal recessive conditions characterized by multiple subcutaneous skin nodules, gingival hypertrophy, joint contractures, and hyaline deposition. We previously mapped the gene for JHF to chromosome 4q21. We now report the identification of 15 different mutations in the gene encoding capillary morphogenesis protein 2 (CMG2) in 17 families with JHF or ISH. CMG2 is a transmembrane protein that is induced during capillary morphogenesis and that binds laminin and collagen IV via a von Willebrand factor type A (vWA) domain. Of interest, CMG2 also functions as a cellular receptor for anthrax toxin. Preliminary genotype-phenotype analyses suggest that abrogation of binding by the vWA domain results in severe disease typical of ISH, whereas in-frame mutations affecting a novel, highly conserved cytoplasmic domain result in a milder phenotype. These data (1) demonstrate that JHF and ISH are allelic conditions and (2) implicate perturbation of basement-membrane matrix assembly as the cause of the characteristic perivascular hyaline deposition seen in these conditions.

Mosaic PPM1D mutations are associated with predisposition to breast and ovarian cancer

Improved sequencing technologies offer unprecedented opportunities for investigating the role of rare genetic variation in common disease. However, there are considerable challenges with respect to study design, data analysis and replication. Using pooled next-generation sequencing of 507 genes implicated in the repair of DNA in 1,150 samples, an analytical strategy focused on protein-truncating variants (PTVs) and a large-scale sequencing case–control replication experiment in 13,642 individuals, here we show that rare PTVs in the p53-inducible protein phosphatase PPM1D are associated with predisposition to breast cancer and ovarian cancer. PPM1D PTV mutations were present in 25 out of 7,781 cases versus 1 out of 5,861 controls (P = 1.12 × 10−5), including 18 mutations in 6,912 individuals with breast cancer (P = 2.42 × 10−4) and 12 mutations in 1,121 individuals with ovarian cancer (P = 3.10 × 10−9). Notably, all of the identified PPM1D PTVs were mosaic in lymphocyte DNA and clustered within a 370-base-pair region in the final exon of the gene, carboxy-terminal to the phosphatase catalytic domain. Functional studies demonstrate that the mutations result in enhanced suppression of p53 in response to ionizing radiation exposure, suggesting that the mutant alleles encode hyperactive PPM1D isoforms. Thus, although the mutations cause premature protein truncation, they do not result in the simple loss-of-function effect typically associated with this class of variant, but instead probably have a gain-of-function effect. Our results have implications for the detection and management of breast and ovarian cancer risk. More generally, these data provide new insights into the role of rare and of mosaic genetic variants in common conditions, and the use of sequencing in their identification.

Constitutional 11p15 abnormalities, including heritable imprinting center mutations, cause nonsyndromic Wilms tumor

Constitutional abnormalities at the imprinted 11p15 growth regulatory region cause syndromes characterized by disordered growth, some of which include a risk of Wilms tumor. We explored their possible contribution to nonsyndromic Wilms tumor and identified constitutional 11p15 abnormalities in genomic lymphocyte DNA from 13 of 437 individuals (3%) with sporadic Wilms tumor without features of growth disorders, including 12% of bilateral cases (P = 0.001) and in one familial Wilms tumor pedigree. No abnormality was detected in 220 controls (P = 0.006). Abnormalities identified included H19 DMR epimutations, uniparental disomy 11p15 and H19 DMR imprinting center mutations (one microinsertion and one microdeletion), thus identifying microinsertion as a new class of imprinting center mutation. Our data identify constitutional 11p15 defects as one of the most common known causes of Wilms tumor, provide mechanistic insights into imprinting disruption and reveal clinically important epigenotype-phenotype associations. The impact on clinical management dictates that constitutional 11p15 analysis should be considered in all individuals with Wilms tumor.

Mutations in the DNA methyltransferase gene, DNMT3A, cause an overgrowth syndrome with intellectual disability

Overgrowth disorders are a heterogeneous group of conditions characterized by increased growth parameters and other variable clinical features such as intellectual disability and facial dysmorphism. To identify new causes of human overgrowth, we performed exome sequencing in ten proband-parent trios and detected two de novo DNMT3A mutations. We identified 11 additional de novo mutations by sequencing DNMT3A in a further 142 individuals with overgrowth. The mutations alter residues in functional DNMT3A domains, and protein modeling suggests that they interfere with domain-domain interactions and histone binding. Similar mutations were not present in 1,000 UK population controls (13/152 cases versus 0/1,000 controls; P < 0.0001). Mutation carriers had a distinctive facial appearance, intellectual disability and greater height. DNMT3A encodes a DNA methyltransferase essential for establishing methylation during embryogenesis and is commonly somatically mutated in acute myeloid leukemia. Thus, DNMT3A joins an emerging group of epigenetic DNA- and histone-modifying genes associated with both developmental growth disorders and hematological malignancies.Overgrowth disorders are a heterogeneous group of conditions characterized by increased growth parameters and other variable clinical features such as intellectual disability and facial dysmorphism. To identify new causes of human overgrowth, we performed exome sequencing in ten proband-parent trios and detected two de novo DNMT3A mutations. We identified 11 additional de novo mutations by sequencing DNMT3A in a further 142 individuals with overgrowth. The mutations alter residues in functional DNMT3A domains, and protein modeling suggests that they interfere with domain-domain interactions and histone binding. Similar mutations were not present in 1,000 UK population controls (13/152 cases versus 0/1,000 controls; P < 0.0001). Mutation carriers had a distinctive facial appearance, intellectual disability and greater height. DNMT3A encodes a DNA methyltransferase essential for establishing methylation during embryogenesis and is commonly somatically mutated in acute myeloid leukemia. Thus, DNMT3A joins an emerging group of epigenetic DNA- and histone-modifying genes associated with both developmental growth disorders and hematological malignancies.

Mutations in CEP57 cause mosaic variegated aneuploidy syndrome

Using exome sequencing and a variant prioritization strategy that focuses on loss-of-function variants, we identified biallelic, loss-of-function CEP57 mutations as a cause of constitutional mosaic aneuploidies. CEP57 is a centrosomal protein and is involved in nucleating and stabilizing microtubules. Our findings indicate that these and/or additional functions of CEP57 are crucial for maintaining correct chromosomal number during cell division.