Erik Björck

Genetic variation in ICF syndrome: evidence for genetic heterogeneity.

ICF syndrome is a rare autosomal recessive immunoglobulin deficiency, sometimes combined with defective cellular immunity. Other features that are frequently observed in ICF syndrome patients include facial dysmorphism, developmental delay, and recurrent infections. The most diagnostic feature of ICF syndrome is the branching of chromosomes 1, 9, and 16 due to pericentromeric instability. Positional candidate cloning recently discovered the de novo DNA methyltransferase 3B (DNMT3B) as the responsible gene by identifying seven different mutations in nine ICF patients. DNMT3B specifically methylates repeat sequences adjacent to the centromeres of chromosome 1, 9, and 16. Our panel of 14 ICF patients was subjected to mutation analysis in the DNMT3B gene. Mutations in DNMT3B were discovered in only nine of our 14 ICF patients. Moreover, two ICF patients from consanguineous families who did not show autozygosity (i.e. homozygosity by descent) for the DNMT3B locus did not reveal DNMT3B mutations, suggesting genetic heterogeneity for this disease. Mutation analysis revealed 11 different mutations, including seven novel ones: eight different missense mutations, two different nonsense mutations, and a splice‐site mutation leading to the insertion of three aa’s. The missense mutations occurred in or near the catalytic domain of DNMT3B protein, indicating a possible interference with the normal functioning of the enzyme. However, none of the ICF patients was homozygous for a nonsense allele, suggesting that absence of this enzyme is not compatible with life. Compound heterozygosity for a missense and a nonsense mutation did not seem to correlate with a more severe phenotype. Hum Mutat 16:509–517, 2000.

Ovarian cancer linked to Lynch syndrome typically presents as early-onset, non-serous epithelial tumors.

OBJECTIVE Heredity is a major cause of ovarian cancer and during recent years the contribution from germline mismatch repair (MMR) gene mutations linked to Lynch syndrome has gradually been recognized. METHODS We characterized clinical features, tumor morphology and mismatch repair defects in all ovarian cancers identified in Swedish and Danish Lynch syndrome families. RESULTS In total, 63 epithelial ovarian cancers developed at mean 48 (range 30-79) years of age with 47% being early stage (FIGO stage I). Histologically, endometrioid (35%) and clear cell (17%) tumors were overrepresented. The underlying MMR gene mutations in these families affected MSH2 in 49%, MSH6 in 33% and MLH1 in 17%. Immunohistochemical loss of the corresponding MMR protein was demonstrated in 33/36 (92%) tumors analyzed. CONCLUSION The combined data from our cohorts demonstrate that ovarian cancer associated with Lynch syndrome typically presents at young age as early-stage, non-serous tumors, which implicates that a family history of colorectal and endometrial cancer should be specifically considered in such cases.

Stickler syndrome caused by COL2A1 mutations: Genotype-phenotype correlation in a series of 100 patients

Stickler syndrome is an autosomal dominant connective tissue disorder caused by mutations in different collagen genes. The aim of our study was to define more precisely the phenotype and genotype of Stickler syndrome type 1 by investigating a large series of patients with a heterozygous mutation in COL2A1. In 188 probands with the clinical diagnosis of Stickler syndrome, the COL2A1 gene was analyzed by either a mutation scanning technique or bidirectional fluorescent DNA sequencing. The effect of splice site alterations was investigated by analyzing mRNA. Multiplex ligation-dependent amplification analysis was used for the detection of intragenic deletions. We identified 77 different COL2A1 mutations in 100 affected individuals. Analysis of the splice site mutations showed unusual RNA isoforms, most of which contained a premature stop codon. Vitreous anomalies and retinal detachments were found more frequently in patients with a COL2A1 mutation compared with the mutation-negative group (P<0.01). Overall, 20 of 23 sporadic patients with a COL2A1 mutation had either a cleft palate or retinal detachment with vitreous anomalies. The presence of vitreous anomalies, retinal tears or detachments, cleft palate and a positive family history were shown to be good indicators for a COL2A1 defect. In conclusion, we confirm that Stickler syndrome type 1 is predominantly caused by loss-of-function mutations in the COL2A1 gene as >90% of the mutations were predicted to result in nonsense-mediated decay. On the basis of binary regression analysis, we developed a scoring system that may be useful when evaluating patients with Stickler syndrome.

Mantle cell lymphomas acquire increased expression of CCL4, CCL5 and 4-1BB-L implicated in cell survival.

We have analyzed mantle cell lymphomas (MCLs), using high‐density DNA microarrays, and confirmed the expression of differentially regulated antigens, using flow cytometry and immunohistochemistry. The results show that MCLs acquire expression of molecules that normally are involved in interaction with other immune cells and, thus, might affect the ability of the tumor to survive. The MCL signature is represented by the overexpression of the chemokine CCL4 (MIP‐1β), implicated in the recruitment of regulatory T cells, as well as CCL5 and 4‐1BB‐L. The latter molecules are normally involved in chemotaxis of T cells and B cell activation, respectively. Signaling through 4‐1BB‐L allows B cells to proliferate and the expression of its ligand, by the intra‐tumoral mesh of follicular dendritic cells (FDC), could thus serve as a paracrine loop facilitating growth and survival of MCL cells.

Mutation screening of fumarate hydratase by multiplex ligation-dependent probe amplification: detection of exonic deletion in a patient with leiomyomatosis and renal cell cancer

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a syndrome predisposing to cutaneous and uterine leiomyomatosis as well as renal cell cancer and uterine leiomyosarcoma. Heterozygous germline mutations in the fumarate hydratase (FH, fumarase) gene are known to cause HLRCC. On occasion, no FH mutation is detected by direct sequencing, despite the evident HLRCC phenotype in a family. In the present study, to investigate whole gene or exonic deletions and amplifications in FH mutation-negative patients, we used multiplex ligation-dependent probe amplification technology. The study material comprised 7 FH mutation-negative HLRCC patients and 12 patients affected with HLRCC-associated phenotypes, including papillary RCC, early-onset RCC, uterine leiomyomas, or uterine leiomyosarcoma. A novel FH mutation, a deletion of FH exon 1 that encodes the mitochondrial signal peptide, was detected in one of the HLRCC patients (1/7). The patient with the FH mutation displayed numerous painful cutaneous leiomyomas and papillary type renal cell cancer. Our finding, together with the two patients with whole FH gene deletion who had been detected previously, suggests that exonic or whole-gene FH deletions are not a frequent cause of HLRCC syndrome.

No evidence for a genetic modifier for renal cell cancer risk in HLRCC syndrome

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. Cutaneous and uterine leiomyomas are the most common clinical manifestations of HLRCC, whereas only approximately 20% of the families display renal cell cancer (RCC). The number of RCC cases in these families varies from one to five. Interestingly, families with multiple RCC cases are mainly found in Finland and the USA. Such aggregation of RCC in only some families and populations has led to the hypothesis that besides FH mutations also other inherited genetic and/or environmental factors may contribute to the malignant kidney tumor formation. To search for such a genetic modifier we have performed a genome-wide linkage analysis in two and an identical by descent analysis in four Finnish HLRCC families with several RCC patients. Additional Finnish and French families were used in fine-mapping and haplotype analyses. The only region compatible with linkage was the locus surrounding the FH gene itself in chromosome 1q43. The genes in the putative candidate region were screened, but no potentially pathogenic alterations were observed. Although these data do not rule out the existence of a genetic modifier, they emphasize the contribution of the FH genotype in HLRCC related RCC. Therefore, as all FH mutation carriers may have an increased risk for developing renal cancer, counseling and genetic testing should be offered for all HLRCC family members and clinical follow-up should be organized for the mutation carriers.

Prevalence of colonic neoplasia and advanced lesions in the normal population : a prospective population-based colonoscopy study.

Abstract Objective. There are few prospective studies of the prevalence of colonic neoplasia in the normal population. In order to properly evaluate screening-protocols for colorectal cancer in risk groups (e.g., older subjects or those with a family history), it is essential to know the prevalence of adenomas and cancer in the normal population. Methods. A prospective population-based colonoscopy study on 745 individuals born in Sweden aged 19–70 years was conducted (mean age 51.1 years). All polyps seen were retrieved and examined. Results. Out of the 745 individuals 27% had polyps, regardless of kind. Adenomas were found in 10% of the individuals and finding of adenomas was positively correlated to higher age. Men had adenomas in 15% and women in 6% of the cases. Women had a right-sided dominance of adenomas. Hyperplastic polyps were seen in 21% of the individuals. The presence of hyperplastic polyps was significantly positively correlated to the presence of adenomas. Advanced adenomas were seen in 2.8% of the study participants, but no cancers were detected. Conclusion. One in 10 healthy subjects had an adenoma but advanced adenomas were uncommon. Men and women have a different adenoma prevalence and localization. The results provide baseline European data for evaluating colonoscopy screening-protocols for colorectal cancer risk groups, and the findings may have implications for colon cancer screening in the normal, otherwise-healthy population.

HAX-1 expression in human B lymphoma.

HS-1-associated protein X-1 (HAX-1) was originally identified as a 35 kDa protein that interacts with HS-1, a Src kinase substrate, and was suggested to have a role in B-cell signal transduction. HAX-1 is ubiquitously expressed in murine and human tissues and seems to be predominantly localized to mitochondria, and to a lesser extent to the endoplasmic reticulum and nuclear membrane. Previous studies have disclosed homozygous mutations in the HAX1 gene in patients with the autosomal recessive form of severe congenital neutropenia or Kostmann disease, indicating a critical role for HAX-1 in the regulation of myeloid progenitor cell survival in the bone marrow. More recent studies point to a critical role of HAX-1 in B-cell development, at least in mice. HAX-1 was initially suggested to display homology with BCL-2, and several studies have implicated HAX-1 in the regulation of apoptosis. HAX-1 may also have a role in cell migration, which in turn could have implications for the invasive activity and metastatic potential of cancer cells. However, despite its ubiquitous expression and apparent roles in cell death and cell migration, very few studies have investigated the expression of HAX-1 in human tumors, and the expression of HAX-1 in hematopoietic malignancies is unknown. Therefore, we studied the pattern of expression of HAX1 mRNA in human cancer using publically available transcriptomics databases. Gene expression profiling is a powerful strategy for improved understanding of the underlying pathogenesis and biology of lymphomas. Several studies have generated gene signatures that can classify and differentiate sub-groups of lymphomas and some signatures were also predictive for survival and treatment response. For instance, our previous study using transcriptomic profiling of a set of follicular lymphomas identified a six-gene profile that associated with favorable outcome and response to CHOP (cyclophosphamide, vincristine, doxorubicin and prednisone). The recent collection of large sets of public microarray data into databases has become a valuable tool for initial exploration of genes across thousands of samples of normal and cancer tissues. We determined the expression of HAX1 in two public transcriptomics databases, the in silico transcriptomics (IST) database that contains data from 9.783 Affymetrix gene expression analyses of 43 normal tissues, 68 cancer types and 64 other diseases, and the recently developed human gene expression map derived from 5.372 samples of 369 different cell and tissue types including various disease states. Using the IST database, we noted that HAX1 was highly expressed in particular in B-cell-related hematopoietic malignancies, including plasma-cell leukemia and B-cell lymphomas (Figure 1a, and see Figure 2a for HAX1 expression in all tumor types). Interrogation of the human gene expression map, which includes 96 biological groups, showed that HAX1 was significantly overexpressed in hematological neoplasms such as anaplastic large cell lymphoma, as well as in breast ductal carcinoma (Figure 1b). Furthermore, HAX1 expression was low in chronic myeloid leukemia and acute lymphoblastic leukemia (Figure 1a). For comparison, we also assessed the expression of BCL2 in the two public transcriptomics databases (Figure 1a, for hematopoietic malignancies, and see Figures 1b and 2b for all tumor types, based on the IST and human gene expression map databases). Next, we examined the expression of HAX-1 protein in a series of paraffin-embedded diagnostic samples from 50 patients with B-cell lymphoma (Table 1) retrieved from archives of the Department of Pathology, Karolinska University Hospital, Stockholm. Diagnosis was established according to the WHO 2008 classification. The diagnosis of Burkitt’s lymphoma was confirmed by fluorescence in situ hybridization for the t(8;14) translocation. The panel included six follicular (FC) lymphoma samples selected from a previously published cohort that we have studied using microarray gene expression profiling. On the basis of the microarray data, we selected three samples with

Dystrophia Helsinglandica: a new type of hereditary corneal recurrent erosions with late subepithelial fibrosis

Purpose:  To describe the phenotype of an autosomal‐dominant corneal dystrophy with an early onset of recurrent corneal erosions and development of subepithelial fibrosis in the cornea, and also to exclude genetic linkage to known corneal dystrophies with autosomal‐dominant inheritance and clinical resemblance.

A new corneal disease with recurrent erosive episodes and autosomal-dominant inheritance

Purpose:  The aim of this study was to characterize the phenotype in a large family with autosomal‐dominant recurrent corneal erosions, and also to exclude genetic linkage to known autosomal‐dominant inherited corneal dystrophies with clinical resemblance.