Molecular characterization of a common fragile site (FRA7H) on human chromosome 7 by the cloning of a simian virus 40 integration site

Common fragile sites are chromosomal loci prone to breakage and rearrangement, hypothesized to provide targets for foreign DNA integration. We cloned a simian virus 40 integration site and showed by fluorescent in situ hybridization analysis that the integration event had occurred within a common aphidicolin-induced fragile site on human chromosome 7, FRA7H. A region of 161 kb spanning FRA7H was defined and sequenced. Several regions with a potential unusual DNA structure, including high-flexibility, low-stability, and non-B-DNA-forming sequences were identified in this region. We performed a similar analysis on the published FRA3B sequence and the putative partial FRA7G, which also revealed an impressive cluster of regions with high flexibility and low stability. Thus, these unusual DNA characteristics are possibly intrinsic properties of common fragile sites that may affect their replication and condensation as well as organization, and may lead to fragility.

Neurturin exerts potent actions on survival and function of midbrain dopaminergic neurons

Glial cell line-derived neurotrophic factor (GDNF) exhibits potent effects on survival and function of midbrain dopaminergic (DA) neurons in a variety of models. Although other growth factors expressed in the vicinity of developing DA neurons have been reported to support survival of DA neurons in vitro, to date none of these factors duplicate the potent and selective actions of GDNF in vivo. We report here that neurturin (NTN), a homolog of GDNF, is expressed in the nigrostriatal system, and that NTN exerts potent effects on survival and function of midbrain DA neurons. Our findings indicate that NTN mRNA is sequentially expressed in the ventral midbrain and striatum during development and that NTN exhibits survival-promoting actions on both developing and mature DA neurons. In vitro, NTN supports survival of embryonic DA neurons, and in vivo, direct injection of NTN into the substantia nigra protects mature DA neurons from cell death induced by 6-OHDA. Furthermore, administration of NTN into the striatum of intact adult animals induces behavioral and biochemical changes associated with functional upregulation of nigral DA neurons. The similarity in potency and efficacy of NTN and GDNF on DA neurons in several paradigms stands in contrast to the differential distribution of the receptor components GDNF Family Receptor alpha1 (GFRalpha1) and GFRalpha2 within the ventral mesencephalon. These results suggest that NTN is an endogenous trophic factor for midbrain DA neurons and point to the possibility that GDNF and NTN may exert redundant trophic influences on nigral DA neurons acting via a receptor complex that includes GFRalpha1.

GFRalpha1 is an essential receptor component for GDNF in the developing nervous system and kidney

Glial cell line-derived neurotrophic factor (GDNF) is a distant member of the TGFbeta protein family that is essential for neuronal survival and renal morphogenesis. We show that mice who are deficient in the glycosyl-phosphatidyl inositol (GPI) -linked protein GFRalpha1 (GDNFRalpha) display deficits in the kidneys, the enteric nervous system, and spinal motor and sensory neurons that are strikingly similar to those of the GDNF- and Ret-deficient mice. GFRalpha1-deficient dopaminergic and nodose sensory ganglia neurons no longer respond to GDNF or to the structurally related protein neurturin (NTN) but can be rescued when exposed to GDNF or neurturin in the presence of soluble GFRalpha1. In contrast, GFRalpha1-deficient submandibular parasympathetic neurons retain normal response to these two factors. Taken together with the available genetic and biochemical data, these findings support the idea that GFRalpha1 and the transmembrane tyrosine kinase Ret are both necessary receptor components for GDNF in the developing kidney and nervous system, and that GDNF and neurturin can mediate some of their activities through a second receptor.

An L-type calcium-channel gene mutated in incomplete X-linked congenital stationary night blindness

The locus for the incomplete form of X-linked congenital stationary night blindness (CSNB2) maps to a 1.1-Mb region in Xp11.23 between markers DXS722 and DXS255. We identified a retina-specific calcium channel alpha1-subunit gene (CACNA1F) in this region, consisting of 48 exons encoding 1966 amino acids and showing high homology to L-type calcium channel alpha1-subunits. Mutation analysis in 13 families with CSNB2 revealed nine different mutations in 10 families, including three nonsense and one frameshift mutation. These data indicate that aberrations in a voltage-gated calcium channel, presumably causing a decrease in neurotransmitter release from photoreceptor presynaptic terminals, are a frequent cause of CSNB2.

Ovarian cancer screening

Despite advances in molecular biology, surgical oncology, and chemotherapy, the prognosis for ovarian cancer remains poor. The excellent survival rates for stage I disease provide the rationale for efforts to screen for early-stage ovarian cancer. However, there are doubts about the feasibility of screening related to the natural history of the disease, the performance of the available tests, and health economic considerations. The investigators use the World Health Organization criteria for a screening program as a framework for discussing current issues in ovarian cancer screening. These include screening modalities and strategies, high- and low-risk populations, and the acceptability, psychological impact, and cost of screening. As a result of developments during the last decade, there are now real prospects for practical and effective ovarian cancer screening programs. Research to date has made important progress, but information about the impact of screening on mortality from ovarian cancer is still awaited. Three large randomized controlled trials of ovarian cancer screening are currently recruiting volunteers and will yield important results in the next few years.

FGF and Shh signals control dopaminergic and serotonergic cell fate in the anterior neural plate

During development, distinct classes of neurons are specified in precise locations along the dorso-ventral and anterior-posterior axes of the neural tube. We provide evidence that intersections of Shh, which is expressed along the ventral neural tube, and FGF8, which is locally produced at the mid/hindbrain boundary and in the rostral forebrain, create induction sites for dopaminergic neurons in the midbrain and forebrain. The same intersection, when preceded by a third signal, FGF4, which is expressed in the primitive streak, defines an inductive center for hindbrain 5-HT neurons. These findings illustrate that cell patterning in the neural plate is a multistep process in which early inducers, which initially divide the neural plate into crude compartments, are replaced by multiple local organizing centers, which specify distinct neuronal cell types within these compartments.

Nibrin, a novel DNA double-strand break repair protein, is mutated in Nijmegen breakage syndrome

Nijmegen breakage syndrome (NBS) is an autosomal recessive chromosomal instability syndrome characterized by microcephaly, growth retardation, immunodeficiency, and cancer predisposition. Cells from NBS patients are hypersensitive to ionizing radiation with cytogenetic features indistinguishable from ataxia telangiectasia. We describe the positional cloning of a gene encoding a novel protein, nibrin. It contains two modules found in cell cycle checkpoint proteins, a forkhead-associated domain adjacent to a breast cancer carboxy-terminal domain. A truncating 5 bp deletion was identified in the majority of NBS patients, carrying a conserved marker haplotype. Five further truncating mutations were identified in patients with other distinct haplotypes. The domains found in nibrin and the NBS phenotype suggest that this disorder is caused by defective responses to DNA double-strand breaks.

Effect of moderate bone hyperthermia on cell viability and mechanical function

Extracorporeal hyperthermia treatment of bone followed by its reimplantation may be an optional treatment of bone tumors. In this study, the authors examined the minimal hyperthermic condition in which complete eradication of all viable cells in rat bone can be achieved and the mechanical effect of this treatment on the tested bone. When the results were evaluated histologically by special lactate dehydrogenase activity staining, it was found that complete bone cell death occurred after 30 minutes of heating at 60 degrees C. Cartilage cells, including those of the epiphysis, were more resistant to thermal damage. When the ability of the specimens to proliferate in cell cultures was tested, no growth was observed after heating at temperatures of 50 degrees C or greater. The mechanical stiffness tested in the Instron machine showed decreased bone stiffness at 70 degrees C but no change in the breaking load of the bones. Controlled hyperthermia's ability to eradicate viable cells without significant damage to the mechanical properties may have clinical relevance in limb salvage tumor surgery.

The neural cell adhesion molecule L1: genomic organisation and differential splicing is conserved between man and the pufferfish Fugu

The human gene for the neural cell adhesion molecule L1 is located on Xq28 between the ALD and MeCP2 loci. Mutations in the L1 gene are associated with four related neurological disorders, X-linked hydrocephalus, spastic paraplegia (SPG1), MASA syndrome, and X-linked corpus callosum agenesis. The clinical relevance of L1 has led us to sequence the L1 gene in human and to investigate its conservation in the vertebrate model genome of the pufferfish, Fugu rubripes (Fugu), a species with a compact genome of around 40Mb. For this purpose we have sequenced a human and a Fugu cosmid clone containing the corresponding L1 genes. For comparison, we have also amplified and sequenced the complete Fugu L1 cDNA. We find that the genomic structure of L1 is conserved. The human and Fugu L1 gene both have 28 exons of nearly identical size. Differential splicing of exons 2 and 27 is conserved over 430 million years, the evolutionary time span between the teleost Fugu and the human L1 gene. In contrast to previously published Fugu genes, many introns are larger in the Fugu L1 gene, making it slightly larger in size despite the compact nature of the Fugu genome. Homology at the amino acid and the nucleotide level with 40% and 51%, respectively, is lower than that of any previously reported Fugu gene. At the level of protein structure, both human and Fugu L1 molecules are composed of six immunoglobulin (Ig)-like domains and five fibronectin (Fn) type III domains, followed by a transmembrane domain and a short cytoplasmic domain. Only the transmembrane and the cytoplasmic domains are significantly conserved in Fugu, supporting their proposed function in intracellular signalling and interaction with cytoskeletal elements in the process of neurite outgrowth and fascicle formation. Our results show that the cytoplasmic domain can be further subdivided into a conserved and a variable region, which may correspond to different functions. Most pathological missense mutations in human L1 affect conserved residues. Fifteen out of 22 reported missense mutations alter amino acids that are identical in both species.

Calcium-dependent Ret activation by GDNF and neurturin

Glial cell line-derived neurotrophic factor (GDNF) and neurturin (NTN) define a new family of neurotrophic factors that play crucial roles in survival and differentiation of various neurons. Recent studies demonstrated that GDNF and NTN use a multicomponent receptor system in which glycosyl-phosphatidylinositol (GPI)-linked cell surface proteins and Ret receptor tyrosine kinase function as the ligand-binding and signalling components, respectively. In the present study, we investigated the role of Ca2+ ions for biochemical and biological activities of Ret because Ret has a unique structure of the extracellular domain with the cadherin-like motif. The results demonstrated that Ca2+ ions might be required for the complex formation of Ret and GDNF or NTN that induces Ret oligomerization and autophosphorylation. Full morphological differentiation of neuroblastoma cells by these neurotrophic factors was also Ca2+-dependent. These findings thus suggested that, in addition to GPI-linked cell surface proteins, Ca2+ ions are components of the signal transducing complex formed by Ret and GDNF protein family.

Activating Smoothened mutations in sporadic basal-cell carcinoma

Basal-cell carcinomas (BCCs) are the commonest human cancer. Insight into their genesis came from identification of mutations in the PATCHED gene (PTCH) in patients with the basal-cell nevus syndrome, a hereditary disease characterized by multiple BCCs and by developmental abnormalities. The binding of Sonic hedgehog (SHH) to its receptor, PTCH, is thought to prevent normal inhibition by PTCH of Smoothened (SMO), a seven-span transmembrane protein. According to this model, the inhibition of SMO signalling is relieved following mutational inactivation of PTCH in basal-cell nevus syndrome. We report here the identification of activating somatic missense mutations in the SMO gene itself in sporadic BCCs from three patients. Mutant SMO, unlike wild type, can cooperate with adenovirus E1A to transform rat embryonic fibroblast cells in culture. Furthermore, skin abnormalities similar to BCCs developed in transgenic murine skin overexpressing mutant SMO. These findings support the role of SMO as a signalling component of the SHH-receptor complex and provide direct evidence that mutated SMO can function as an oncogene in BCCs.

Human renin binding protein: complete genomic sequence and association of an intronic T/C polymorphism with the prorenin level in males

The role of renin binding protein (RnBP) in human (patho)physiology, despite its biochemical characterization, is as yet unclear. RnBP has been shown to bind and inactivate renin, a key player of the blood pressure regulating renin-angiotensin system. This renders the RnBP gene a promising candidate gene in human hypertension. Herein, a molecular genetic approach was employed to investigate if RnBP might affect renin, prorenin and/or blood pressure levels. Sequencing of the human Xq28 chromosomal region provided the precise chromosomal location and full genomic sequence of the RnBP gene. All 11 exons, adjacent intronic splice sites and the promoter region were sequenced in 20 patients with essential hypertension of early onset and possible X-linked inheritance and in four normotensive individuals. The only variant found was a single base exchange polymorphism 61 base pairs upstream of the intron 6/exon 7 boundary (T61C). Several cardiovascular parameters, the renin, and prorenin levels and the T61C allele status were determined in 505 Caucasian individuals. Male individuals without medication who were hemizygous for the C allele were characterized by lower prorenin levels (196 +/- 15 versus 256 +/- 12 mU/l, P = 0.05) and a significantly higher renin/prorenin ratio (10.7 +/- 1.5 versus 7.7 +/- 0.3%, P = 0.002), whereas no variations in circulating renin, blood pressure, heart rate and left ventricular mass index were associated with the C allele. No significant association was observed in women. The data do not exclude a role of RnBP in essential hypertension. The complete genomic structure of the RnBP gene, including the identified repetitive sequence elements, provides an essential tool for further studies of the RnBP gene in hypertensive patients with a different genetic background.

Genomic organization of two novel genes on human Xq28: compact head to head arrangement of IDH gamma and TRAP delta is conserved in rat and mouse

In this paper we present the entire genomic sequence as well as the cDNA sequence of two new human genes encoding the gamma subunit of the NAD(+)-dependent isocitrate dehydrogenase (H-IDH gamma) and the translocon-associated protein delta subunit (TRAP delta). These genes are located on region q28 of the human X chromosome, approximately 70 kb telomeric to the adrenoleukodystrophy locus (ALD). The sequences of the transcripts of both genes were obtained by searching the EST database with genomic data. Identified ESTs were completely sequenced and assembled to cDNAs comprising the entire coding region. For IDH gamma, several EST clones indicate differential splicing. IDH gamma and TRAP delta are arranged in a compact head to head manner. The nontranscribed intergenic region represents only 133 bp and is embedded in a CpG island. The CpG island obviously functions as a bidirectional promoter to initiate the transcription of both functionally unrelated genes with quite distinct expression patterns. This exceptional gene arrangement prompted us to clone and sequence genomic DNA fragments containing the homologous intergenic regions of rat and mouse. We show that in both species this area is similarly compact and represents less than 249 bp in rat and not more than 164 bp in mouse. In both cases this intergenic region is embedded in a CpG island and is highly conserved with nucleotide identity values ranging from 70.1% between human and rat to 92.6% between mouse and rat.

Genomic structure of a novel LIM domain gene (ZNF185) in Xq28 and comparisons with the orthologous murine transcript

Construction of a transcript map in the DXS52 region in Xq28 had previously led to the isolation of a cDNA with a LIM zinc finger domain in the carboxyl terminus. In parallel, the orthologous murine transcript was isolated from the syntenic region. The human and mouse cDNAs have been designated ZNF185 and Zfp185, respectively. By integrating the cDNA sequence with the cosmid-derived genomic sequence the exon-intron structure of the 3' end of the ZNF185 gene was resolved. Comparative sequence analyses of the human genomic sequence with the full-length murine cDNA facilitated prediction of the 5' end of the gene. The selective expression of three transcripts corresponding to the ZNF185 gene and a related gene was shown by Northern and Southern blots. In situ hybridizations revealed a nonubiquitous and stage-specific expression of Zfp185, especially in differentiating connective tissue. Since LIM proteins regulate cellular proliferation and/or differentiation by diverse mechanisms, and some have directly been associated with disease, conceivably ZNF185 may represent a candidate for a disease-causing gene linked to Xq28. Knowledge of the genomic structure will permit detailed mutation analyses.

Control of cell pattern in the neural tube by the zinc finger transcription factor and oncogene Gli-1

Sonic hedgehog (Shh) is a putative morphogen secreted by the floor plate and notochord, which specifies the fate of multiple cell types in the ventral aspect of the vertebrate nervous system. Since in Drosophila the actions of Hh have been shown to be transduced by Cubitus interruptus (Ci), a zinc finger transcription factor, we examined whether a vertebrate homolog of this protein can mediate the functions of Shh in the vertebrate nervous system. Here, we demonstrate that expression of Gli-1, one of three vertebrate homologs of Ci, can be induced by Shh in the neural tube. Further, ectopic expression of Gli-1 in the dorsal midbrain and hindbrain of transgenic mice mimics the effects of ectopically expressed Shh-N, leading to the activation of ventral neural tube markers such as Ptc, HNF-3beta, and Shh; to the suppression of dorsal markers such as Pax-3 and AL-1; and to the formation of ectopic dorsal clusters of dopaminergic and serotonergic neurons. These findings demonstrate that GLI-1 can reproduce the cell patterning actions of Shh in the developing nervous system and provide support for the hypothesis that it is a mediator of the Shh signal in vertebrates.

Evidence that perihypoglossal neurons involved in vestibular-auditory and gaze control functions respond to nerve growth factor

Nerve growth factor (NGF), which has long been considered to be a trophic factor for peripheral sensory and sympathetic neurons, has been found recently to influence cholinergic neurons in the basal forebrain and neostriatum. In the present study, we provide evidence that brainstem neurons in the perihypoglossal area that relay information from the inner ear and vestibular apparatus to the cerebellum and tectum are responsive to NGF. These neurons, which are located in the nucleus prepositus hypoglossi (NPH), spinal vestibular nucleus, cochlear complex, and gigantocellular and paragigantocellular nuclei of the reticular formation, express functional receptors for NGF and up-regulate the expression of trkA receptors after injection of NGF into targets. In addition, the developmental up-regulation of NGF in the cerebellum coincides with the differentiation of the perihypoglossal nuclei. These results suggest that neurons representing the principal brain relays for auditory and vestibular pathways and perihypoglossal neurons involved in gaze coordination are a novel group of central neurons (besides cholinergic neurons in the basal forebrain and neostriatum) that respond to NGF.

A GPI-linked protein that interacts with Ret to form a candidate neurturin receptor

Glial-cell-line-derived neurotrophic factor (GDNF) and neurturin (NTN) are two structurally related, potent survival factors for sympathetic, sensory and central nervous system neurons. GDNF mediates its actions through a multicomponent receptor system composed of a ligand-binding glycosyl-phosphatidylinositol (GPI)-linked protein (designated GDNFR-alpha) and the transmembrane protein tyrosine kinase Ret. In contrast, the mechanism by which the NTN signal is transmitted is not well understood. Here we describe the identification and tissue distribution of a GPI-linked protein (designated NTNR-alpha) that is structurally related to GDNFR-alpha. We further demonstrate that NTNR-alpha binds NTN (K[d] approximately 10 pM) but not GDNF with high affinity; that GDNFR-alpha binds to GDNF but not NTN with high affinity; and that cellular responses to NTN require the presence of NTNR-alpha. Finally, we show that NTN, in the presence of NTNR-alpha, induces tyrosine-phosphorylation of Ret, and that NTN, NTNR-alpha and Ret form a physical complex on the cell surface. These findings identify Ret and NTNR-alpha as signalling and ligand-binding components, respectively, of a receptor for NTN and define a novel family of receptors for neurotrophic and differentiation factors composed of a shared transmembrane protein tyrosine kinase and a ligand-specific GPI-linked protein.

Neurturin responsiveness requires a GPI-linked receptor and the Ret receptor tyrosine kinase

Neurturin (NTN) is a recently identified homologue of glial-cell-line-derived neurotrophic factor (GDNF). Both factors promote the survival of a variety of neurons, and GDNF is required for the development of the enteric nervous system and kidney. GDNF signals through a receptor complex consisting of the receptor tyrosine kinase Ret and a glycosyl-phosphatidylinositol (GPI)-linked receptor termed GDNFR-alpha. Here we report the cloning of a new GPI-linked receptor termed NTNR-alpha that is homologous with GDNFR-alpha and is widely expressed in the nervous system and other tissues. By using microinjection to introduce expression plasmids into neurons, we show that coexpression of NTNR-alpha with Ret confers a survival response to neurturin but not GDNF, and that coexpression of GDNFR-alpha with Ret confers a survival response to GDNF but not neurturin. Our findings indicate that GDNF and neurturin promote neuronal survival by signalling through similar multicomponent receptors that consist of a common receptor tyrosine kinase and a member of a GPI-linked family of receptors that determines ligand specificity.

Ataxia-telangiectasia locus: sequence analysis of 184 kb of human genomic DNA containing the entire ATM gene

Ataxia-telangiectasia (A-T) is an autosomal recessive disorder involving cerebellar degeneration, immunodeficiency, chromosomal instability, radiosensitivity, and cancer predisposition. The genomic organization of the A-T gene, designated ATM, was established recently. To date, more than 100 A-T-associated mutations have been reported in the ATM gene that do not support the existence of one or several mutational hotspots. To allow genotype/phenotype correlations it will be important to find additional ATM mutations. The nature and location of the mutations will also provide insights into the molecular processes that underly the disease. To facilitate the search for ATM mutations and to establish the basis for the identification of transcriptional regulatory elements, we have sequenced and report here 184,490 bp of genomic sequence from the human 11q22-23 chromosomal region containing the entire ATM gene, spanning 146 kb, and 10 kb of the 5'-region of an adjacent gene named E14/NPAT. The latter shares a bidirectional promoter with ATM and is transcribed in the opposite direction. The entire region is transcribed to approximately 85% and translated to 5%. Genome-wide repeats were found to constitute 37.2%, with LINE (17.1%) and Alu (14.6%) being the main repetitive elements. The high representation of LINE repeats is attributable to the presence of three full-length LINE-1s, inserted in the same orientation in introns 18 and 63 as well as downstream of the ATM gene. Homology searches suggest that ATM exon 2 could have derived from a mammalian interspersed repeat (MIR). Promoter recognition algorithms identified divergent promoter elements within the CpG island, which lies between the ATM and E14/NPAT genes, and provide evidence for a putative second ATM promoter located within intron 3, immediately upstream of the first coding exon. The low G+C level (38.1%) of the ATM locus is reflected in a strongly biased codon and amino acid usage of the gene.

Molecular basis of symbiosis between Rhizobium and legumes

Access to mineral nitrogen often limits plant growth, and so symbiotic relationships have evolved between plants and a variety of nitrogen-fixing organisms. These associations are responsible for reducing 120 million tonnes of atmospheric nitrogen to ammonia each year. In agriculture, independence from nitrogenous fertilizers expands crop production and minimizes pollution of water tables, lakes and rivers. Here we present the complete nucleotide sequence and gene complement of the plasmid from Rhizobium sp. NGR234 that endows the bacterium with the ability to associate symbiotically with leguminous plants. In conjunction with transcriptional analyses, these data demonstrate the presence of new symbiotic loci and signalling mechanisms. The sequence and organization of genes involved in replication and conjugal transfer are similar to those of Agrobacterium, suggesting a recent lateral transfer of genetic information.

Ataxia-telangiectasia: structural diversity of untranslated sequences suggests complex post-transcriptional regulation of ATM gene expression

Mutations in the ATM gene are responsible for the multisystem disorder ataxia-telangiectasia, characterized by neurodegeneration, immune deficiency and cancer predisposition. While no alternative splicing was identified within the coding region, the first four exons of the ATM gene, which fall within the 5'untranslated region (UTR), undergo extensive alternative splicing. We identified 12 different 5'UTRs that show considerable diversity in length and sequence contents. These mRNA leaders, which range from 150 to 884 nucleotides (nt), are expected to form variable secondary structures and contain different numbers of AUG codons. The longest 5'UTR contains a total of 18 AUGs upstream of the translation start site. The 3'UTR of 3590 nt is contained within a single 3'exon. Alternative polyadenylation results in 3'UTRs of varying lengths. These structural features suggest that ATM expression might be subject to complex post-transcriptional regulation, enabling rapid modulation of ATM protein level in response to environmental stimuli or alterations in cellular physiological states.

Pseudoautosomal deletions encompassing a novel homeobox gene cause growth failure in idiopathic short stature and Turner syndrome

Growth retardation resulting in short stature is a major concern for parents and due to its great variety of causes, a complex diagnostic challenge for clinicians. A major locus involved in linear growth has been implicated within the pseudoautosomal region (PAR1) of the human sex chromosomes. We have determined an interval of 170 kb of DNA within PAR1 which was deleted in 36 individuals with short stature and different rearrangements on Xp22 or Yp11.3. This deletion was not detected in any of the relatives with normal stature or in a further 30 individuals with rearrangements on Xp22 or Yp11.3 with normal height. We have isolated a homeobox-containing gene (SHOX) from this region, which has at least two alternatively spliced forms, encoding proteins with different patterns of expression. We also identified one functionally significant SHOX mutation by screening 91 individuals with idiopathic short stature. Our data suggest an involvement of SHOX in idiopathic growth retardation and in the short stature phenotype of Turner syndrome patients.

Reversal of protein-losing enteropathy with heparin therapy in three patients with univentricular hearts and Fontan palliation

We studied three pediatric patients with protein-losing enteropathy in conjunction with univentricular hearts and right atrial to pulmonary artery anastomosis (Fontan operation) before and during heparin therapy. Each patient showed dramatic improvements in symptoms, marked elevations in serum albumin levels, and quantitative reversal of enteric protein loss within a few weeks of beginning therapy. These findings suggest that heparin may be an important treatment for this poorly understood condition.

The tumour-suppressor gene patched encodes a candidate receptor for Sonic hedgehog

The protein Sonic hedgehog (Shh) controls patterning and growth during vertebrate development. Here we demonstrate that it binds Patched (vPtc), which has been identified as a tumour-suppressor protein in basal cell carcinoma, with high affinity. We show that Ptc can form a physical complex with a newly cloned vertebrate homologue of the Drosophila protein Smoothened (vSmo), and that vSmo is coexpressed with vPtc in many tissues but does not bind Shh directly. These findings, combined with available genetic evidence from Drosophila, support the hypothesis that Ptc is a receptor for Shh, and that vSmo could be a signalling component that is linked to Ptc.

Mesenchymal chondrosarcoma of the cerebellum

Mesenchymal chondrosarcoma is a rare malignant neoplasm of bone and soft tissues. An unique case is described of an 8-year-old child with a midline cerebellar lesion. Pertinent clinical and radiologic findings along with histopathologic features are described. To our knowledge, this is the first case of mesenchymal chondrosarcoma arising in the cerebellar parenchyma of a child.

Anatomic, histologic, and magnetic resonance imaging abnormalities of the shoulder

Six fresh frozen, human cadaver shoulders were evaluated for gross anatomic, magnetic resonance imaging, and histologic abnormalities. The shoulders underwent routine magnetic resonance imaging with and without intraarticular Gadolinium using a standard surface shoulder coil. The shoulders were dissected in a systematic fashion to yield 18 anatomic specimens from the supraspinatus and infraspinatus tendon as well as the glenoid labrum. These specimens were studied histologically using hematoxylin and eosin and Goldner's trichrome stains. Gross anatomic and magnetic resonance image abnormalities of the rotator cuff corresponded to histologic changes consistent with tendon degeneration. However, there was a poor correlation between gross anatomic, magnetic resonance image, and histologic changes of degeneration in the glenoid labrum. In general, histologic degeneration was more severe than abnormalities seen either grossly or on magnetic resonance images.

The genomic organization of a human creatine transporter (CRTR) gene located in Xq28

During the course of a large-scale sequencing project in Xq28, a human creatine transporter (CRTR) gene was discovered. The gene is located approximately 36 kb centromeric to ALD. The gene contains 13 exons and spans about 8.5 kb of genomic DNA. Since the creatine transporter has a prominent function in muscular physiology, it is a candidate gene for Barth syndrome and infantile cardiomyopathy mapped to Xq28.

Selection for genes encoding secreted proteins and receptors

Extracellular proteins play an essential role in the formation, differentiation, and maintenance of multicellular organisms. Despite that, the systematic identification of genes encoding these proteins has not been possible. We describe here a highly efficient method to isolate genes encoding secreted and membrane-bound proteins by using a single-step selection in yeast. Application of this method, termed signal peptide selection, to various tissues yielded 559 clones that appear to encode known or novel extracellular proteins. These include members of the transforming growth factor and epidermal growth factor protein families, endocrine hormones, tyrosine kinase receptors, serine/threonine kinase receptors, seven transmembrane receptors, cell adhesion molecules, extracellular matrix proteins, plasma proteins, and ion channels. The eventual identification of most, or all, extracellular signaling molecules will advance our understanding of fundamental biological processes and our ability to intervene in disease states.

Characterization of a multicomponent receptor for GDNF

Glial-cell-line-derived neurotrophic factor (GDNF) is a potent survival factor for central and peripheral neurons, and is essential for the development of kidneys and the enteric nervous system. Despite the potential clinical and physiological importance of GDNF, its mechanism of action is unknown. Here we show that physiological responses to GDNF require the presence of a novel glycosyl-phosphatidylinositol (GPI)-linked protein (designated GDNFR-alpha) that is expressed on GDNF-responsive cells and binds GDNF with a high affinity. We further demonstrate that GDNF promotes the formation of a physical complex between GDNFR-alpha and the orphan tyrosin kinase receptor Ret, thereby inducing its tyrosine phosphorylation. These findings support the hypothesis that GDNF uses a multi-subunit receptor system in which GDNFR-alpha and Ret function as the ligand-binding and signalling components, respectively.

Renal and neuronal abnormalities in mice lacking GDNF

Glial cell-line derived neurotrophic factor (GDNF) is a potent survival factor for embryonic midbrain dopaminergic, spinal motor, cranial sensory, sympathetic, and hindbrain noradrenergic neurons, and is available to these cells in vivo. It is therefore considered a physiological trophic factor and a potential therapeutic agent for Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. Here we show that at postnatal day 0 (P0), GDNF-deficient mice have deficits in dorsal root ganglion, sympathetic and nodose neurons, but not in hindbrain noradrenergic or midbrain dopaminergic neurons. These mice completely lack the enteric nervous system (ENS), ureters and kidneys. Thus GDNF is important for the development and/or survival of enteric, sympathetic and sensory neurons and the renal system, but is not essential for catecholaminergic neurons in the central nervous system (CNS).

Sequencing the 500-kb GC-rich symbiotic replicon of Rhizobium sp. NGR234 using dye terminators and a thermostable "sequenase": a beginning

Genomes of the soil-borne nitrogen-fixing symbionts of legumes [Azo(Brady)Rhizobium species] typically have GC contents of 59-65 mol%. As a consequence, compressions (up to 400 per cosmid) are common using automated dye primer shotgun sequencing methods. To overcome this difficulty, we have exclusively applied dye terminators in combination with a thermostable "sequenase" for shotgun sequencing GC-rich cosmids from pNGR234a, the 500-kbp symbiotic replicon of Rhizobium sp. NGR234. A thermostable sequenase incorporates dye terminators into DNA more efficiently than Taq DNA polymerase, thus reducing the concentrations needed (20- to 250-fold). Unincorporated dye terminators can simply be removed by ethanol precipitation. Here, we present data of pXB296, one of 23 overlapping cosmids representing pNGR234a. We demonstrate that the greatly reduced number of compressions results in a much faster assembly of cosmid sequence data by comparing assembly of the shotgun data from pXB296 and the data from another pNGR234a cosmid (pXB110) sequenced using dye primer methods. Within the 34,010-bp sequence from pXB296, 28 coding regions were predicted. All of them showed significant homologies to known proteins, including oligopeptide permeases, an essential cluster for nitrogen fixation, and the C4-dicarboxylate transporter DctA.

Cardiotrophin-1, a cytokine present in embryonic muscle, supports long-term survival of spinal motoneurons

The muscle-derived factors required for survival of embryonic motoneurons are not clearly identified. Cardiotrophin-1 (CT-1), a cytokine related to ciliary neurotrophic factor (CNTF), is expressed at high levels in embryonic limb bud and is secreted by differentiated myotubes. In vitro, CT-1 kept 43% of purified E14 rat motoneurons alive for 2 weeks (EC50 = 20 pM). In vivo, CT-1 protected neonatal sciatic motoneurons against the effects of axotomy. CT-1 action on motoneurons was inhibited by phosphatidylinositol-specific phospholipase C (PIPLC), suggesting that CT-1 may act through a GPI-linked component. Since no binding of CT-1 to CNTFR alpha was detected, CT-1 may use a novel cytokine receptor alpha subunit. CT-1 may be important in normal motoneuron development and as a potential tool for slowing motoneuron degeneration in human diseases.

Identification of a gene disrupted by a microdeletion in a patient with X-linked retinitis pigmentosa (XLRP)

The gene for the most frequent from of X-linked retinitis pigmentosa (XLRP), RP3, has been assigned by genetic and physical mapping to a segment of less than 1000 kbp, which is flanked by the marker DXS1110 and the ornithine transcarbamylase (OTC) gene. In search of microdeletions, we have screened the DNA of 30 unrelated patients with XLRP by employing a representative set of YAC-derived DNA fragments that were generated by restriction enzyme digestion and PCR amplification. In one of these patients, a 6.4 kbp microdeletion was detected which was not present in the DNA of 444 male controls. A cosmid contig spanning the deletion was constructed and used to isolate cDNAs from retina-specific libraries. Exons corresponding to these expressed sequences as well as other putative exons were identified by sequencing more than 30 kbp of the critical region. So far, no point mutations in these putative exon sequences have been identified.

Genomic Organization of the ATM gene

The ATM gene was recently identified and found to be responsible for the genetic disorder ataxiatelgiectasia. The major ATM transcript is 13 kb. Using long-distance PCR, we determined the genomic structure of this gene and identified all of its exon-intron boundaries. The ATM gene spans approximately 150 kb of genomic DNA and consists of 66 exons. The initiation codon falls within exon 4. The last exon is 3.8 kb and contains the stop codon and a 3'-untranslated region of about 3600 nucleotides.

Transforming growth factor-beta 3, glial cell line-derived neurotrophic factor, and fibroblast growth factor-2, act in different manners to promote motoneuron survival in vitro

Developing chick motoneurons depend on as yet unidentified factors from the periphery and the central nervous system for their survival. Using cultures of purified embryonic motoneurons, we show that basic fibroblast growth factor (FGF-2) or transforming growth factor-beta 3 (TGF beta 3) each have only low survival-promoting activity when tested alone, but act synergistically to keep motoneurons alive for at least 3 days. Glial cell line-derived neurotrophic factor (GDNF), another member of the TGF beta family, was itself sufficient to maintain a population of motoneurons. However, its effect was not significantly increased by the addition of FGF-2. These results suggest that FGF-2, TGF beta 3, and GDNF, which are all present in the environment of developing motoneurons, may act different mechanisms as physiological survival factors for this population of central neurons.

Transition of aortic endothelial cells from resting to migrating cells is associated with three sequential patterns of microfilament organization

The endothelial cell is unique because it must undergo a transition from a resting cell with a cytoskeleton organized for barrier function to one which promotes cell translocation following denuding endothelial injury. Since actin microfilaments are critical for both maintaining the integrity of the resting monolayer and for optimum reendothelialization, we carried out a detailed study of the organization of microfilaments as the cell undergoes the transition from a resting to a translocating cell. We used an in vitro model in which a linear wound was made in a confluent monolayer of porcine aortic endothelial cells. The complex reorganization of actin microfilament bundles following injury and their relationship to microtubules and vinculin was studied in cells at the wound edge using immunofluorescent scanning laser confocal microscopy and time-lapse videomicroscopy. In the resting confluent monolayer, microfilaments were present as a dense peripheral band (DPB) located toward the upper part of the cell and as central microfilament bundles at the substratum. Three distinct stages of microfilament reorganization occurred sequentially during early repair. Stage 1 followed wounding and involved the reduction of the DPBs of microfilaments and associated peripheral cell-cell vinculin plaques. This was associated with rapid forward actin-based lamellipodia extrusions and cell elongation. Low-dose cytochalasin, which did not disrupt the morphology of microfilament bundles, reduced elongation. Stage 2 was characterized by central microfilaments behind the lamellipodia distributed parallel to the wound edge with vinculin plaques at their tips. This was associated with prominent spreading at the front of the cell which enhanced the extent of coverage of the denuded wound area. Stage 3 was characterized by the orientation of central microfilaments perpendicular to the wound edge with vinculin plaques at their tips and was associated with the initiation of cell translocation. There was no specific structural association between central microfilaments and microtubules as the former were toward the substratum while the latter were toward the center and upper part of the cell. Thus, the sequential appearance of three patterns of microfilament distribution define the cytoskeletal events that regulate the reestablishment of endothelial integrity following denuding endothelial injury.

Neurotrophin-4/5 postpones the death of injured spinal motoneurons in newborn rats

We have compared the short- and long-term effects of Neurotrophin-4/5 (NT-4/5) on the survival of spinal motoneurons in neonatal rats. To this aim, the sciatic nerve was cut in newborn rats and NT-4/5 or buffer were applied to the proximal nerve stem in a gelfoam as well as by daily local injection. The number of motoneurons or ventral root fibers was determined 4, 11, and 14 days later. Four days after received NT-4/5 lost only 19% + 2.7% (540 + 81). No systemic effect on the contralateral motoneurons was observed. Surprisingly, 11 and 14 days following the operation, the loss of motoneurons and of ventral root fibers was the same in buffer and NT-4/5 treated animal despite the daily treatment. Thus, although NT-4/5 is a potent survival factor for motoneurons in culture and can transiently prevent the death of motoneurons in vivo, it can not, under these experimental conditions, permanently rescue lesioned motoneurons. These results indicate that other trophic factors or combinations of factors may be required to permanently prevent the death of spinal motoneurons and that the short term survival promoting effects of neurotropic factors in motoneuron lesion models can not be used to predict their therapeutic potential in chronic neurodegenerative disorders.

Malnutrition in hospitalized children with congenital heart disease

OBJECTIVE

To determine the prevalence of malnutrition among hospitalized children with congenital heart disease by age, disease process, and clinical status.

DESIGN

Cross-sectional, retrospective chart review.

SETTING

Pediatric cardiology units at a 150-bed tertiary care teaching hospital in Ann Arbor, Mich.

PATIENTS

Patients (n = 160) were randomly selected from consecutive admissions to the Pediatric Cardiology and Thoracic Surgery Services during a 1-year period.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Acute and chronic malnutrition, assessed by comparing the patients' weight and height with established means.

RESULTS

Acute and chronic malnutrition occurred in 33% and 64% of the patients, respectively. Age, diagnostic category, and symptoms were associated with malnutrition. Eighty percent of infants presented with acute malnutrition compared with 18% of patients of other ages (P < .001). Malnutrition affected 60% of patients with left-to-right shunts, 53% of patients with complex heart disease, and no patients with primary rhythm disturbances. Acute malnutrition affected 11% and chronic malnutrition affected 50% of patients with left-sided heart obstruction. Acute or chronic malnutrition occurred in 70% or more of patients with cyanosis and/or congestive heart failure but in only 30% of patients with neither (P < .001).

CONCLUSION

Malnutrition in hospitalized children with congenital heart disease remains common, highlighting the importance of nutritional screening and intervention.

GDNF is an age-specific survival factor for sensory and autonomic neurons

Glial cell line-derived neurotrophic factor (GDNF) promotes the survival of two populations of CNS neurons: motoneurons and midbrain dopaminergic neurons. To see whether GDNF promotes the survival of PNS neurons, we studied embryonic chicken autonomic and sensory neurons in culture. We show that GDNF promotes the survival of sympathetic, parasympathetic, proprioceptive, enteroceptive, and small and large cutaneous sensory neurons. Whereas sympathetic, parasympathetic, and proprioceptive neurons become less responsive to GDNF with age, enteroceptive and cutaneous sensory neurons become more responsive. GDNF mRNA is expressed in the tissues innervated by these neurons, and developmental changes in its expression in several tissues mirror the changing responses of the innervating neurons to GDNF. These results show that GDNF promotes the survival of multiple PNS and CNS neurons and suggest that GDNF may be important for regulating the survival of various populations of neurons at different stages of their development.

Individualized developmental care for very-low-birth-weight premature infants

Forty very-low-birth-weight neonatal intensive care unit (NICU) infants with birth weights < or = 1,250 g were randomly assigned to treatment or control groups. Behavior of the treatment infants was systematically evaluated, and individualized developmentally oriented care plans were implemented to enhance stability. Treatment babies required fewer days of intermittent mandatory ventilation and continuous positive airway pressure and achieved full enteral feedings sooner. Length of hospital stay and hospital charges were less for treatment than control infants. There were favorable effects on treatment infants' behavioral performance at 42 weeks' postconceptional age. These results support the hypothesis that behaviorally sensitive, developmentally oriented care improves medical and neurodevelopmental outcome in the NICU.

Predictors of 2-year mortality among older male veterans on a geriatric rehabilitation unit

OBJECTIVE

To determine if nutritional parameters and discharge setting are associated with mortality in older male veterans on a Geriatric rehabilitation unit (GRU).

DESIGN

Two-year follow-up of sequential admissions to the GRU who had laboratory studies completed on admission to the acute hospital and on transfer to and discharge from the GRU.

SETTING

University-affiliated VA medical center.

PATIENTS

Eighty-three consecutive older male veterans admitted to the GRU.

MEASUREMENT

Mortality during a period of 2 years post-discharge.

MAIN RESULTS

In a univariate analysis, predictors of mortality were serum albumin level < or = 3.5 g/dL on admission to the GRU (P = .01), moderate or severe Nutritional Status Score (P = .03), discharge to a place other than home (P = .01), and use of antibiotics while on the GRU (P = .05). Discharge albumin remained the single significant predictor of mortality in a multivariate analysis (P = .005).

CONCLUSIONS

Serum albumin is the strongest predictor of 2-year post-hospitalization mortality of older patients cared for on a GRU. Other predictors were presence of infection, Nutritional Status Score of moderate or severe compromise, and discharge to a place other than home.

Immunosuppressive agents and endothelial repair. Prednisolone delays migration and cytoskeletal rearrangement in wounded porcine aortic monolayers

Endothelial denudation at areas of predilection to atherosclerosis is balanced by an active repair process that may be inhibited under conditions of accelerated atherosclerosis. After cardiac transplantation, the accelerated atherosclerotic process that develops may be enhanced by immunosuppressive agents that have nonspecific effects on cell signaling, proliferation, and response to injury. To study subtle effects of cyclosporine A, azathioprine, and 6 alpha-methylprednisolone on normal endothelial repair processes, confluent porcine endothelial monolayers were denuded in the presence of clinically relevant concentrations of these agents. The rate of endothelial wound repair was compared and the effects on cell spreading, proliferation, and the cytoskeleton assessed. 6 alpha-Methylprednisolone at concentrations of 1.25 to 50 mumol/L was associated with a transient 30% to 60% inhibition of endothelial wound repair. This was associated with increased cell size at the wound edge and a delay in centrosomal reorientation toward the wound, without any effect on cell proliferation. Cyclosporine and azathioprine in clinically relevant concentrations did not affect endothelial repair. Thus, corticosteroids transiently inhibit endothelial cytoskeletal alterations that are important in endothelial repair after a denuding injury.

Passive immunization of rhesus macaques against SIV infection and disease

To evaluate the role of humoral immunity against simian immunodeficiency virus (SIV), we tested whether passive immunization with plasma from SIVmac251 vaccine-protected or healthy infected animals would protect rhesus monkeys against intravenous infection with ten 50% animal infectious doses of the cell-free homologous virus. The challenge dose of this SIVmac251 virus stock had previously caused persistent infection in all (21 of 21) nonimmunized controls. A plasma pool was obtained from a donor that had been immunized with an inactivated whole SIVmac251 vaccine produced in human T cells. This plasma pool contained low levels of SIVmac binding and neutralizing antibody but had a high titer of antibodies recognizing human cell proteins. Given 4 or 18 hr before intravenous challenge, this plasma completely protected three of eight recipients from infection and delayed virus detection in one recipient. The five unprotected animals had only a transient or undetectable p27 antigenemia and low virus load in their PBMCs, and all survived at least 7 months after infection. By contrast, no protection was observed in 6 monkeys given inactivated, pooled plasma or purified immunoglobulin (Ig) from healthy SIVmac251-infected animals. This plasma pool and the Ig preparation contained high levels of SIV-binding and neutralizing antibody but no reactivity to human cellular components. Five of the six recipients had persistent antigenemia after challenge and four died acutely from simian AIDS in 4-7 months. These studies suggest that passive transfer of antibody to human cellular antigens can confer protection against SIVmac whereas passive transfer of neutralizing antibodies without human cellular antibodies does not protect against the homologous virus and may enhance infection.

Induction of midbrain dopaminergic neurons by Sonic hedgehog

Midbrain dopaminergic neurons, whose loss in adults results in Parkinson's disease, can be specified during embryonic development by a contact-dependent signal from floor plate cells. Here we show that the amino-terminal product of Sonic hedgehog autoproteolysis (SHH-N), an inductive signal expressed by floor plate cells, can induce dopaminergic neurons in vitro. We show further that manipulations to increase the activity of cyclic AMP-dependent protein kinase A, which is known to antagonize hedgehog signaling, can block dopaminergic neuron induction by floor plate cells. Our results and those of other studies indicate that SHH-N can function in a dose-dependent manner to induce different cell types within the neural tube. Our results also provide the basis for a potential cell transplantation therapy for Parkinson's disease.

Exon 2 of the gene for neural cell adhesion molecule L1 is alternatively spliced in B cells

L1CAM is a neural cell adhesion molecule expressed mainly on neurones' cell surface and plays an important role in the developing fetal brain. Recently, we have shown that mutations in the gene encoding L1CAM are responsible for three related neurological disorders including the most common form of inherited hydrocephalus. During our genetic analysis, we have discovered that L1CAM is also expressed on the surface of B cells but that the messenger RNA in this tissue is different to that in brain through alternative splicing of the L1 gene. This indicates that this region of the L1 molecule has a distinct role in brain cells compared to B lymphocytes and confirms its importance in brain development.

Cardiotrophin-1. Biological activities and binding to the leukemia inhibitory factor receptor/gp130 signaling complex

Cardiotrophin-1 (CT-1) is a newly isolated cytokine that was identified based on its ability to induce cardiac myocyte hypertrophy. It is a member of the family of cytokines that includes interleukins-6 and -11, leukemia inhibitory factor (LIF), ciliary neurotrophic factor, and oncostatin M. These cytokines induce a pleiotropic set of growth and differentiation activities via receptors that use a common signaling subunit, gp130. In this work we determine the activity of CT-1 in six in vitro biological assays and examine the composition of its cell surface receptor. We find that CT-1 is inactive in stimulating the growth of the hybridoma cell line, B9 and inhibits the growth of the mouse myeloid leukemia cell line, M1. CT-1 induces a phenotypic switch in rat sympathetic neurons and promotes the survival of rat dopaminergic and chick ciliary neurons. CT-1 also inhibits the differentiation of mouse embryonic stem cells. CT-1 and LIF cross-compete for binding to M1 cells, Kd [CT-1] approximately 0.7 nM, and this binding is inhibited by an anti-gp130 monoclonal antibody. Both ligands can be specifically cross-linked to a protein on M1 cells with the mobility of the LIF receptor (approximately 200 kDa). In addition, CT-1 binds directly to a purified, soluble form of the LIF receptor in solution (Kd approximately 2 nM). These data show that CT-1 has a wide range of hematopoietic, neuronal, and developmental activities and that it can act via the LIF receptor and the gp130 signaling subunit.