Mutations in DCHS1 Cause Mitral Valve Prolapse

SUMMARY Mitral valve prolapse (MVP) is a common cardiac valve disease that affects nearly 1 in 40 individuals1–3. It can manifest as mitral regurgitation and is the leading indication for mitral valve surgery4,5. Despite a clear heritable component, the genetic etiology leading to non-syndromic MVP has remained elusive. Four affected individuals from a large multigenerational family segregating non-syndromic MVP underwent capture sequencing of the linked interval on chromosome 11. We report a missense mutation in the DCHS1 gene, the human homologue of the Drosophila cell polarity gene dachsous (ds) that segregates with MVP in the family. Morpholino knockdown of the zebrafish homolog dachsous1b resulted in a cardiac atrioventricular canal defect that could be rescued by wild-type human DCHS1, but not by DCHS1 mRNA with the familial mutation. Further genetic studies identified two additional families in which a second deleterious DCHS1 mutation segregates with MVP. Both DCHS1 mutations reduce protein stability as demonstrated in zebrafish, cultured cells, and, notably, in mitral valve interstitial cells (MVICs) obtained during mitral valve repair surgery of a proband. Dchs1+/− mice had prolapse of thickened mitral leaflets, which could be traced back to developmental errors in valve morphogenesis. DCHS1 deficiency in MVP patient MVICs as well as in Dchs1+/− mouse MVICs result in altered migration and cellular patterning, supporting these processes as etiological underpinnings for the disease. Understanding the role of DCHS1 in mitral valve development and MVP pathogenesis holds potential for therapeutic insights for this very common disease

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Evaluation of nimotuzumab Fab2 as an optical imaging agent in EGFR positive cancers

Abstract Molecular-targeted imaging probes can be used with a variety of imaging modalities to detect diseased tissues and guide their removal. EGFR is a useful biomarker for a variety of cancers, because it is expressed at high levels relative to normal tissues. Previously, we showed the anti-EGFR antibody nimotuzumab can be used as a positron emission tomography and fluorescent imaging probe for EGFR positive cancers in mice. These imaging probes are currently in clinical trials for PET imaging and image-guided surgery, respectively. One issue with using antibody probes for imaging is their long circulation time and slow tissue penetration, which requires patients to wait a few days after injection before imaging or surgery, multiple visits and longer radiation exposure. Here, we generated a Fab2 fragment of nimotuzumab, by pepsin digestion and labeled it with IRDye800CW to evaluate its optical imaging properties. The Fab2 had faster tumor accumulation and clearance in mice relative to the nimotuzumab IgG. The fluorescent signal peaked at 2 h post injection and remained high until 6 h post injection. The properties of the Fab2 allow a higher signal to background to be obtained in a shorter time frame, reducing the wait time for imaging after probe infusion

Neurofibromin haploinsufficiency results in altered spermatogenesis in a mouse model of neurofibromatosis type 1.

The fertility of men with neurofibromatosis 1 (NF1) is reduced. Despite this observation, gonadal function has not been examined in patients with NF1. In order to assess the role of reduced neurofibromin in the testes, we examined testicular morphology and function in an Nf1+/- mouse model. We found that although Nf1+/- male mice are able to reproduce, they have significantly fewer pups per litter than Nf1+/+ control males. Reduced fertility in Nf1+/- male mice is associated with disorganization of the seminiferous epithelium, with exfoliation of germ cells and immature spermatids into the tubule lumen. Morphometric analysis shows that these alterations are associated with decreased Leydig cell numbers and increased spermatid cell numbers. We hypothesized that hyper-activation of Ras in Nf1+/- males affects ectoplasmic specialization, a Sertoli-spermatid adherens junction involved in spermiation. Consistent with this idea, we found increased expression of phosphorylated ERK, a downstream effector of Ras that has been shown to alter ectoplasmic specialization, in Nf1+/- males in comparison to control Nf1+/+ littermates. These data demonstrate that neurofibromin haploinsufficiency impairs spermatogenesis and fertility in a mouse model of NF1

Mitochondrial dysfunction reactivates α-fetoprotein expression that drives copper-dependent immunosuppression in mitochondrial disease models

Signaling circuits crucial to systemic physiology are widespread, yet uncovering their molecular underpinnings remains a barrier to understanding the etiology of many metabolic disorders. Here, we identified a copper-linked signaling circuit activated by disruption of mitochondrial function in the murine liver or heart that resulted in atrophy of the spleen and thymus and caused a peripheral white blood cell deficiency. We demonstrated that the leukopenia was caused by alpha-fetoprotein, which required copper and the cell surface receptor CCR5 to promote white blood cell death. We further showed that alpha-fetoprotein expression was upregulated in several cell types upon inhibition of oxidative phosphorylation. Collectively, our data argue that alpha-fetoprotein may be secreted by bioenergetically stressed tissue to suppress the immune system, an effect that may explain the recurrent or chronic infections that are observed in a subset of mitochondrial diseases or in other disorders with secondary mitochondrial dysfunction.Peer reviewe

The sequence and analysis of duplication rich human chromosome 16

We report here the 78,884,754 base pairs of finished human chromosome 16 sequence, representing over 99.9 percent of its euchromatin. Manual annotation revealed 880 protein coding genes confirmed by 1,637 aligned transcripts, 19 tRNA genes, 341 pseudogenes and 3 RNA pseudogenes. These genes include metallothionein, cadherin and iroquois gene families, as well as the disease genes for polycystic kidney disease and acute myelomonocytic leukemia. Several large-scale structural polymorphisms spanning hundreds of kilobasepairs were identified and result in gene content differences across humans. One of the unique features of chromosome 16 is its high level of segmental duplication, ranked among the highest of the human autosomes. While the segmental duplications are enriched in the relatively gene poor pericentromere of the p-arm, some are involved in recent gene duplication and conversion events which are likely to have had an impact on the evolution of primates and human disease susceptibility

The sequence and analysis of duplication-rich human chromosome 16

Human chromosome 16 features one of the highest levels of segmentally duplicated sequence among the human autosomes. We report here the 78,884,754 base pairs of finished chromosome 16 sequence, representing over 99.9% of its euchromatin. Manual annotation revealed 880 protein-coding genes confirmed by 1,670 aligned transcripts, 19 transfer RNA genes, 341 pseudogenes and three RNA pseudogenes. These genes include metallothionein, cadherin and iroquois gene families, as well as the disease genes for polycystic kidney disease and acute myelomonocytic leukaemia. Several large-scale structural polymorphisms spanning hundreds of kilobase pairs were identified and result in gene content differences among humans. Whereas the segmental duplications of chromosome 16 are enriched in the relatively gene-poor pericentromere of the p arm, some are involved in recent gene duplication and conversion events that are likely to have had an impact on the evolution of primates and human disease susceptibility.Joel Martin, Cliff Han, Laurie A. Gordon, Astrid Terry, Shyam Prabhakar, Xinwei She, Gary Xie, Uffe Hellsten, Yee Man Chan, Michael Altherr, Olivier Couronne, Andrea Aerts, Eva Bajorek, Stacey Black, Heather Blumer, Elbert Branscomb, Nancy C. Brown, William J. Bruno, Judith M. Buckingham, David F. Callen, Connie S. Campbell, Mary L. Campbell, Evelyn W. Campbell, Chenier Caoile, Jean F. Challacombe, Leslie A. Chasteen, Olga Chertkov, Han C. Chi, Mari Christensen, Lynn M. Clark, Judith D. Cohn, Mirian Denys, John C. Detter, Mark Dickson, Mira Dimitrijevic-Bussod, Julio Escobar, Joseph J. Fawcett, Dave Flowers, Dea Fotopulos, Tijana Glavina, Maria Gomez, Eidelyn Gonzales, David Goodstein, Lynne A. Goodwin, Deborah L. Grady, Igor Grigoriev, Matthew Groza, Nancy Hammon, Trevor Hawkins, Lauren Haydu, Carl E. Hildebrand, Wayne Huang, Sanjay Israni, Jamie Jett, Phillip B. Jewett, Kristen Kadner, Heather Kimball, Arthur Kobayashi, Marie-Claude Krawczyk, Tina Leyba, Jonathan L. Longmire, Frederick Lopez, Yunian Lou, Steve Lowry, Thom Ludeman, Chitra F. Manohar, Graham A. Mark, Kimberly L. McMurray, Linda J. Meincke, Jenna Morgan, Robert K. Moyzis, Mark O. Mundt, A. Christine Munk, Richard D. Nandkeshwar, Sam Pitluck, Martin Pollard Paul Predki, Beverly Parson-Quintana, Lucia Ramirez, Sam Rash, James Retterer, Darryl O. Ricke, Donna L. Robinson, Alex Rodriguez, Asaf Salamov, Elizabeth H. Saunders, Duncan Scott, Timothy Shough, Raymond L. Stallings, Malinda Stalvey, Robert D. Sutherland, Roxanne Tapia, Judith G. Tesmer, Nina Thayer, Linda S. Thompson, Hope Tice, David C. Torney, Mary Tran-Gyamfi, Ming Tsai, Levy E. Ulanovsky, Anna Ustaszewska, Nu Vo, P. Scott White, Albert L. Williams, Patricia L. Wills, Jung-Rung Wu, Kevin Wu, Joan Yang, Pieter DeJong, David Bruce, Norman A. Doggett, Larry Deaven, Jeremy Schmutz, Jane Grimwood, Paul Richardson, Daniel S. Rokhsar, Evan E. Eichler, Paul Gilna, Susan M. Lucas, Richard M. Myers, Edward M. Rubin and Len A. Pennacchi