Erik Iwarsson

Mutations in amphiphysin 2 ( BIN1 ) disrupt interaction with dynamin 2 and cause autosomal recessive centronuclear myopathy

Centronuclear myopathies are characterized by muscle weakness and abnormal centralization of nuclei in muscle fibers not secondary to regeneration. The severe neonatal X-linked form (myotubular myopathy) is due to mutations in the phosphoinositide phosphatase myotubularin (MTM1), whereas mutations in dynamin 2 (DNM2) have been found in some autosomal dominant cases. By direct sequencing of functional candidate genes, we identified homozygous mutations in amphiphysin 2 (BIN1) in three families with autosomal recessive inheritance. Two missense mutations affecting the BAR (Bin1/amphiphysin/RVS167) domain disrupt its membrane tubulation properties in transfected cells, and a partial truncation of the C-terminal SH3 domain abrogates the interaction with DNM2 and its recruitment to the membrane tubules. Our results suggest that mutations in BIN1 cause centronuclear myopathy by interfering with remodeling of T tubules and/or endocytic membranes, and that the functional interaction between BIN1 and DNM2 is necessary for normal muscle function and positioning of nuclei.

Fetal Membrane Cells for Treatment of Steroid-Refractory Acute Graft-Versus-Host Disease†‡§

The placenta protects the fetus from the mothers immune system. We have previously found that fetal membrane cells (FMCs) isolated from term placenta prevent alloreactivity in vitro. FMCs share many features with bone marrow‐derived mesenchymal stromal cells (MSCs), which we previously introduced to treat severe acute graft‐versus‐host disease (GVHD). Here, we tested FMCs for treatment of steroid‐refractory acute GVHD. After two passages in culture, approximately 109 FMCs were obtained from one single placenta, although not all cells from passage 0 and passage 1 were used for expansion. The FMCs were positive for CD29, CD44, CD73, CD90, CD105, and CD49d but were negative for hematopoietic, endothelial, and epithelial markers. Microsatellite polymorphism analysis showed that FMCs were of maternal origin. All FMCs used showed normal karyotype. Nine patients who had undergone hematopoietic stem cell transplantation (HSCT) and who had developed steroid‐refractory grade III–IV acute GVHD were given 0.9–2.8 × 106 FMCs per kg at 15 infusions. Median age was 57 years. There was no toxicity from infusion of FMCs in eight patients. One patient had seizures after infusion. Two of eight evaluable patients had a complete response and four had a partial response, giving an overall response rate of 75%. Two patients showed no response at all. Three patients are alive from 6 to 21 months after HSCT. One patient is well and two have chronic GVHD. Thus, FMCs may be successfully used for immune modulation and tissue repair. STEM CELLS2013;31:592–601

Analysis of cell-free fetal DNA in maternal blood for detection of trisomy 21, 18 and 13 in a general pregnant population and in a high risk population – a systematic review and meta-analysis

The aim of this study was to review the performance of non‐invasive prenatal testing (NIPT) for detection of trisomy 21, 18 and 13 (T21, T18 and T13) in a general pregnant population as well as to update the data on high‐risk pregnancies.

Amplification-free sequencing of cell-free DNA for prenatal non-invasive diagnosis of chromosomal aberrations.

Cell-free DNA has been used for fetal rhesus factor and sex determination, fetal aneuploidy screening, cancer diagnostics and monitoring, and other applications. However current methods of using cell free DNA require amplification, which leads to allelic dropout and bias especially when starting with small amounts of DNA. Here we describe an amplification-free method for sequencing of cell-free DNA, even from low levels of starting material. We evaluated this method in the context of prenatal diagnosis of fetal aneuploidy and compared it with a PCR-based library preparation method as well as a recently described method using unique molecular identifiers (UMI). All methods performed well, however coverage was increased by the amplification-free method and GC-induced bias was reduced by both the amplification-free method and the UMI method. Future diagnostic applications including whole genome sequencing of cell-free DNA will benefit from amplification-free sequencing.

Novel candidate genes for 46,XY gonadal dysgenesis identified by a customized 1 M array-CGH platform.

Half of all patients with a disorder of sex development (DSD) do not receive a specific molecular diagnosis. Comparative genomic hybridization (CGH) can detect copy number changes causing gene haploinsufficiency or over-expression that can lead to impaired gonadal development and gonadal DSD. The purpose of this study was to identify novel candidate genes for 46,XY gonadal dysgenesis (GD) using a customized 1 M array-CGH platform with whole-genome coverage and probe enrichment targeting 78 genes involved in sex development. Fourteen patients with 46,XY gonadal DSD were enrolled in the study. Nine individuals were analyzed by array CGH. All patients were included in a follow up sequencing study of candidate genes. Three novel candidate regions for 46,XY GD were identified in two patients. An interstitial duplication of the SUPT3H gene and a deletion of C2ORF80 were detected in a pair of affected siblings. Sequence analysis of these genes in all patients revealed no additional mutations. A large duplication highlighting PIP5K1B, PRKACG and FAM189A2 as candidates for 46,XY GD, were also detected. All five genes are expressed in testicular tissues, and one is shown to cause gonadal DSD in mice. However detailed functional information is lacking for these genes.

Positive Attitudes towards Non-Invasive Prenatal Testing (NIPT) in a Swedish Cohort of 1,003 Pregnant Women

Objective The clinical utilization of non-invasive prenatal testing (NIPT) for identification of fetal aneuploidies is expanding worldwide. The aim of this study was to gain an increased understanding of pregnant women’s awareness, attitudes, preferences for risk information and decision-making concerning prenatal examinations with emphasis on NIPT, before its introduction into Swedish healthcare. Method Pregnant women were recruited to fill in a questionnaire, including multiple-choice questions and Likert scales, at nine maternity clinics located in different areas of Stockholm, Sweden. Results In total, 1,003 women participated in the study (86% consent rate). The vast majority (90.7%) considered examinations aiming to detect fetal abnormalities to be good. Regarding NIPT, 59.8% stated that they had heard about the method previously, yet 74.0% would like to use the test if available. The main factor affecting the women’s decision to undergo prenatal chromosomal screening was worry about the baby’s health (82.5%), followed by the urge to have as much information as possible about the fetus (54.5%). Most women (79.9%) preferred to receive NIPT information orally. Conclusion The overwhelming majority of a cohort of 1,003 pregnant women considered prenatal examinations good. Moreover, the majority had a positive attitude towards NIPT and would like to use the test if available.

CBX2 gene analysis in patients with 46,XY and 46,XX gonadal disorders of sex development

OBJECTIVEnTo investigate a cohort of patients with gonadal disorders of sex development (DSD) for causative CBX2 gene mutations and or gene copy number changes.nnnDESIGNnGenetic association study.nnnSETTINGnUniversity laboratory and tertiary university-based referral center.nnnPATIENT(S)n47 patients with different forms of 46,XY or 46,XX gonadal DSD.nnnINTERVENTION(S)nCBX2 gene sequencing and development of a synthetic probe set for multiplex ligation probe amplification (MLPA) to detect CBX2 copy number changes, and reverse-transcriptase polymerase chain reaction (RT-PCR) to evaluate CBX2 expression in two different cell-line types.nnnMAIN OUTCOME MEASURE(S)nGene sequence alteration and or partial or complete gene copy number variations, and detection of CBX2 mRNA isoforms.nnnRESULT(S)nWe detected 10 sequence alterations, 9 reported single nucleotide polymorphisms (SNPs), and a previously unreported variant. This was a silent c.1356G>A transition that may represent a normal variant. A rare SNP (c.1411C>G, p.471Pro>Ala) was found in heterozygous form in one patient. No deletions or duplications were detected by MLPA. Expression of both CBX2 mRNA isoforms was documented in gonadal fibroblasts and Epstein Barr virus (EBV)-transformed lymphocytes.nnnCONCLUSION(S)nNo pathogenic CBX2 mutation was detected. Both CBX2 isoforms are expressed in gonadal fibroblasts and EBV-transformed lymphocytes. This study does not support CBX2 gene disruption as a common cause of gonadal DSD.

Jumping translocation in a phenotypically normal male: A study of mosaicism in spermatozoa, lymphocytes, and fibroblasts.

Both Robertsonian translocations, rob(13;13) and rob(13;15), (in the present case defined as dic(13;15)), are rare chromosomal rearrangements and there is scarce information regarding their behavior during meiosis. In this report we describe a man with mosaicism for two cell lines, each cell line containing a different de novo Robertsonian translocation with the common breakpoint in the centromeric region on chromosome 13. The karyotype was finally defined as: 45,XY,rob(13;13)(q10;q10)[29]/45,XY,dic(13;15)(p11.2;p12)[22], a phenomenon referred to as jumping translocation. The relative occurrence of the two clones in lymphocytes and fibroblasts as well as the meiotic segregation in spermatozoa and the mechanism of formation were studied using karyotype analysis, fluorescence in situ hybridization (FISH), and quantitative fluorescence‐PCR. Karyotype analysis of cultured lymphocytes revealed 57% rob(13;13) cells and 43% dic(13;15) cells and for cultured skin fibroblasts the figures were almost identical (56% and 44%, respectively). FISH analysis showed 55% balanced nuclei for unselected spermatozoa and after swim‐up selection the number of balanced spermatozoa decreased to 41%. In addition, 16% of the unselected spermatozoa and 27% of the spermatozoa after swim‐up selection carried an additional chromosome 13, indicating a high risk for a trisomy 13 offspring. Swim‐up selection did not increase the number of balanced spermatozoa.

Expanding the Clinical Spectrum of Phenotypes Caused by Pathogenic Variants in PLOD2

Osteogenesis imperfecta (OI) is a strikingly heterogeneous group of disorders with a broad range of phenotypic variations. It is also one of the differential diagnoses in bent bone dysplasias along with campomelic dysplasia and thanatophoric dysplasia and can usually be distinguished by decreased bone mineralization and bone fractures. Bent bone dysplasias also include syndromes such as kyphomelic dysplasia (MIM:211350) and mesomelic dysplasia Kozlowski‐Reardon (MIM249710), both of which have been under debate regarding whether or not they are a real entity or simply a phenotypic manifestation of another dysplasia including OI. Bruck syndrome type 2 (BRKS2; MIM:609220) is a rare form of autosomal recessive OI caused by biallelic PLOD2 variants and is associated with congenital joint contractures with pterygia. In this report, we present six patients from four families with novel PLOD2 variants. All cases had multiple fractures. Other features ranged from prenatal lethal severe angulation of the long bones as in kyphomelic dysplasia and mesomelic dysplasia Kozlowski‐Reardon through classical Bruck syndrome to moderate OI with normal joints. Two siblings with a kyphomelic dysplasia‐like phenotype who were stillborn had compound heterozygous variants in PLOD2 (p.Asp585Val and p.Ser166*). One infant who succumbed at age 4 months had a bent bone phenotype phenotypically like skeletal dysplasia Kozlowski‐Reardon (with mesomelic shortening, camptodactyly, retrognathia, cleft palate, skin dimples, but also with fractures). He was homozygous for the nonsense variant (p.Trp561*). Two siblings had various degrees of Bruck syndrome caused by the homozygous missense variant, p.His687Arg. Furthermore a boy with a clinical presentation of moderate OI had a possibly pathogenic homozygous variant p.Trp588Cys. Our experience of six patients with biallelic pathogenic variants in PLOD2 expands the phenotypic spectrum in the PLOD2‐related phenotypes.

Fetal Calcifications Are Associated with Chromosomal Abnormalities

Objective The biological importance of calcifications occasionally noted in fetal tissues (mainly liver) at autopsy or ultrasound is largely unexplored. Previous reports hint at an association to infection, circulatory compromise, malformations or chromosomal abnormalities. To identify factors associated with calcifications, we have performed a case-control study on the largest cohort of fetuses with calcifications described thus far. Methods One-hundred and fifty-one fetuses with calcifications and 302 matched controls were selected from the archives of the Department of Pathology, Karolinska University Hospital. Chromosome analysis by karyotyping or quantitative fluorescence-polymerase chain reaction was performed. Autopsy and placenta reports were scrutinized for presence of malformations and signs of infection. Results Calcifications were mainly located in the liver, but also in heart, bowel, and other tissues. Fetuses with calcifications showed a significantly higher proportion of chromosomal abnormalities than controls; 50% vs. 20% (p<0.001). The most frequent aberrations among cases included trisomy 21 (33%), trisomy 18 (22%), and monosomy X (18%). A similar distribution was seen among controls. When comparing cases and controls with chromosomal abnormalities, the cases had a significantly higher prevalence of malformations (95% vs. 77%, p=0.004). Analyzed the other way around, cases with malformations had a significantly higher proportion of chromosomal abnormalities compared with controls, (66% vs. 31%, p<0.001). Conclusion The presence of fetal calcifications is associated with high risk of chromosomal abnormality in combination with malformations. Identification of a calcification together with a malformation at autopsy more than doubles the probability of detecting a chromosomal abnormality, compared with identification of a malformation only. We propose that identification of a fetal tissue calcification at autopsy, and potentially also at ultrasound examination, should infer special attention towards co-existence of malformations, as this would be a strong indicator for a chromosomal abnormality.