A recurrent de novo mutation in ACTG1 causes isolated ocular coloboma

Ocular coloboma (OC) is a defect in optic fissure closure and is a common cause of severe congenital visual impairment. Bilateral OC is primarily genetically determined and shows marked locus heterogeneity. Whole-exome sequencing (WES) was used to analyze 12 trios (child affected with OC and both unaffected parents). This identified de novo mutations in 10 different genes in eight probands. Three of these genes encoded proteins associated with actin cytoskeleton dynamics: ACTG1, TWF1, and LCP1. Proband-only WES identified a second unrelated individual with isolated OC carrying the same ACTG1 allele, encoding p.(Pro70Leu). Both individuals have normal neurodevelopment with no extra-ocular signs of Baraitser-Winter syndrome. We found this mutant protein to be incapable of incorporation into F-actin. The LCP1 and TWF1 variants each resulted in only minor disturbance of actin interactions, and no further plausibly causative variants were identified in these genes on resequencing 380 unrelated individuals with OC.

A Restricted Repertoire of De Novo Mutations in ITPR1 Cause Gillespie Syndrome with Evidence for Dominant-Negative Effect

Gillespie syndrome (GS) is characterized by bilateral iris hypoplasia, congenital hypotonia, non-progressive ataxia, and progressive cerebellar atrophy. Trio-based exome sequencing identified de novo mutations in ITPR1 in three unrelated individuals with GS recruited to the Deciphering Developmental Disorders study. Whole-exome or targeted sequence analysis identified plausible disease-causing ITPR1 mutations in 10/10 additional GS-affected individuals. These ultra-rare protein-altering variants affected only three residues in ITPR1: Glu2094 missense (one de novo, one co-segregating), Gly2539 missense (five de novo, one inheritance uncertain), and Lys2596 in-frame deletion (four de novo). No clinical or radiological differences were evident between individuals with different mutations. ITPR1 encodes an inositol 1,4,5-triphosphate-responsive calcium channel. The homo-tetrameric structure has been solved by cryoelectron microscopy. Using estimations of the degree of structural change induced by known recessive- and dominant-negative mutations in other disease-associated multimeric channels, we developed a generalizable computational approach to indicate the likely mutational mechanism. This analysis supports a dominant-negative mechanism for GS variants in ITPR1. In GS-derived lymphoblastoid cell lines (LCLs), the proportion of ITPR1-positive cells using immunofluorescence was significantly higher in mutant than control LCLs, consistent with an abnormality of nuclear calcium signaling feedback control. Super-resolution imaging supports the existence of an ITPR1-lined nucleoplasmic reticulum. Mice with Itpr1 heterozygous null mutations showed no major iris defects. Purkinje cells of the cerebellum appear to be the most sensitive to impaired ITPR1 function in humans. Iris hypoplasia is likely to result from either complete loss of ITPR1 activity or structure-specific disruption of multimeric interactions.

Monoallelic and biallelic mutations in MAB21L2 cause a spectrum of major eye malformations

We identified four different missense mutations in the single-exon gene MAB21L2 in eight individuals with bilateral eye malformations from five unrelated families via three independent exome sequencing projects. Three mutational events altered the same amino acid (Arg51), and two were identical de novo mutations (c.151C>T [p.Arg51Cys]) in unrelated children with bilateral anophthalmia, intellectual disability, and rhizomelic skeletal dysplasia. c.152G>A (p.Arg51His) segregated with autosomal-dominant bilateral colobomatous microphthalmia in a large multiplex family. The fourth heterozygous mutation (c.145G>A [p.Glu49Lys]) affected an amino acid within two residues of Arg51 in an adult male with bilateral colobomata. In a fifth family, a homozygous mutation (c.740G>A [p.Arg247Gln]) altering a different region of the protein was identified in two male siblings with bilateral retinal colobomata. In mouse embryos, Mab21l2 showed strong expression in the developing eye, pharyngeal arches, and limb bud. As predicted by structural homology, wild-type MAB21L2 bound single-stranded RNA, whereas this activity was lost in all altered forms of the protein. MAB21L2 had no detectable nucleotidyltransferase activity in vitro, and its function remains unknown. Induced expression of wild-type MAB21L2 in human embryonic kidney 293 cells increased phospho-ERK (pERK1/2) signaling. Compared to the wild-type and p.Arg247Gln proteins, the proteins with the Glu49 and Arg51 variants had increased stability. Abnormal persistence of pERK1/2 signaling in MAB21L2-expressing cells during development is a plausible pathogenic mechanism for the heterozygous mutations. The phenotype associated with the homozygous mutation might be a consequence of complete loss of MAB21L2 RNA binding, although the cellular function of this interaction remains unknown.

Kdm3a lysine demethylase is an Hsp90 client required for cytoskeletal rearrangements during spermatogenesis

The lysine demethylase Kdm3a (Jhdm2a, Jmjd1a) is required for male fertility, sex determination, and metabolic homeostasis through its nuclear role in chromatin remodeling. Many histone-modifying enzymes have additional nonhistone substrates, as well as nonenzymatic functions, contributing to the full spectrum of events underlying their biological roles. We present two Kdm3a mouse models that exhibit cytoplasmic defects that may account in part for the globozoospermia phenotype reported previously. Electron microscopy revealed abnormal acrosome and manchette and the absence of implantation fossa at the caudal end of the nucleus in mice without Kdm3a demethylase activity, which affected cytoplasmic structures required to elongate the sperm head. We describe an enzymatically active new Kdm3a isoform and show that subcellular distribution, protein levels, and lysine demethylation activity of Kdm3a depended on Hsp90. We show that Kdm3a localizes to cytoplasmic structures of maturing spermatids affected in Kdm3a mutant mice, which in turn display altered fractionation of β-actin and γ-tubulin. Kdm3a is therefore a multifunctional Hsp90 client protein that participates directly in the regulation of cytoskeletal components.

Subfunctionalization of duplicated zebrafish pax6 genes by cis-regulatory divergence

Gene duplication is a major driver of evolutionary divergence. In most vertebrates a single PAX6 gene encodes a transcription factor required for eye, brain, olfactory system, and pancreas development. In zebrafish, following a postulated whole-genome duplication event in an ancestral teleost, duplicates pax6a and pax6b jointly fulfill these roles. Mapping of the homozygously viable eye mutant sunrise identified a homeodomain missense change in pax6b, leading to loss of target binding. The mild phenotype emphasizes role-sharing between the co-orthologues. Meticulous mapping of isolated BACs identified perturbed synteny relationships around the duplicates. This highlights the functional conservation of pax6 downstream (3') control sequences, which in most vertebrates reside within the introns of a ubiquitously expressed neighbour gene, ELP4, whose pax6a-linked exons have been lost in zebrafish. Reporter transgenic studies in both mouse and zebrafish, combined with analysis of vertebrate sequence conservation, reveal loss and retention of specific cis-regulatory elements, correlating strongly with the diverged expression of co-orthologues, and providing clear evidence for evolution by subfunctionalization.

Long-range downstream enhancers are essential for Pax6 expression

Pax6 is a developmental control gene with an essential role in development of the eye, brain and pancreas. Pax6, as many other developmental regulators, depends on a substantial number of cis-regulatory elements in addition to its promoters for correct spatiotemporal and quantitative expression. Here we report on our analysis of a set of mice transgenic for a modified yeast artificial chromosome carrying the human PAX6 locus. In this 420 kb YAC a tauGFP-IRES-Neomycin reporter cassette has been inserted into the PAX6 translational start site in exon 4. The YAC has been further engineered to insert LoxP sites flanking a 35 kb long, distant downstream regulatory region (DRR) containing previously described DNaseI hypersensitive sites, to allow direct comparison between the presence or absence of this region in the same genomic context. Five independent transgenic lines were obtained that vary in the extent of downstream PAX6 locus that has integrated. Analysis of transgenic embryos carrying full-length and truncated versions of the YAC indicates the location and putative function of several novel tissue-specific enhancers. Absence of these distal regulatory elements abolishes expression in specific tissues despite the presence of more proximal enhancers with overlapping specificity, strongly suggesting interaction between these control elements. Using plasmid-based reporter transgenic analysis we provide detailed characterization of one of these enhancers in isolation. Furthermore, we show that overexpression of a short PAX6 isoform derived from an internal promoter in a multicopy YAC transgenic line results in a microphthalmia phenotype. Finally, direct comparison of a single-copy line with the floxed DRR before and after Cre-mediated deletion demonstrates unequivocally the essential role of these long-range control elements for PAX6 expression.

Conserved elements in Pax6 intron 7 involved in (auto)regulation and alternative transcription

Pax6 is a transcription factor with an essential role in eye, central nervous system, and pancreas development. Its expression pattern is restricted to these specific domains within the developing embryo. Here four conserved elements are identified in Pax6 intron 7, showing a high level of sequence conservation between human, mouse, pufferfish, and zebrafish. Three of these are shown to act as cis-regulatory elements, directing expression of a reporter gene to distinct subsets of the Pax6 expression domain. CE1 regulates gene expression in late eye development, CE2 drives expression in the diencephalon and in the developing heart tube where Pax6 is not normally expressed, while CE3 directs expression in rhombencephalon. CE2 is shown to be autoregulated in the diencephalon, responding to absence of Pax6. We identify a highly conserved Pax6 recognition site and demonstrate its ability to bind Pax6 specifically. CE1 is embedded in a CpG island, and we identify a novel Pax6 transcript which initiates from this region. Functional analysis of evolutionary conserved sequences pinpoints novel cis-acting elements that govern the regulation of the complex spatio-temporal and quantitative expression of Pax6.

Toxicological aspects of treatment to remove cyanobacterial toxins from drinking water determined using the heterozygous P53 transgenic mouse model

The presence of toxic cyanobacteria in drinking water reservoirs renders the need to develop treatment methods for the 'safe' removal of their associated toxins. Chlorine has been shown to successfully remove a range of cyanotoxins including microcystins, cylindrospermopsin and saxitoxins. Each cyanotoxin requires specific treatment parameters, particularly solution pH and free chlorine residual. However, currently there has not been any investigation into the toxicological effect of solutions treated for the removal of these cyanotoxins by chlorine. Using the P53(def) transgenic mouse model male and female C57BL/6J hybrid mice were used to investigate potential cancer inducing effects from such oral dosing solutions. Both purified cyanotoxins and toxic cell-free extract cyanobacterial solutions were chlorinated and administered over 90 and 170 days (respectively) in drinking water. No increase in cancer was found in any treatment. The parent cyanotoxins, microcystins, cylindrospermopsin and saxitoxins were readily removed by chlorine. There was no significant increase in the disinfection by-products trihalomethanes or haloacetic acids, levels found were well below guideline values. Histological examination identified no effect of treatment solutions except male mice treated with chlorinated cylindrospermopsin (as a cell free extract). In this instance 40% of males were found to have fatty vacuolation in their livers, cause unknown. It is recommended that further toxicology be undertaken on chlorinated cyanobacterial solutions, particularly for non-genotoxic carcinogenic compounds, for example the Tg. AC transgenic mouse model.

Characterization of a novel gene adjacent to PAX6, revealing synteny conservation with functional significance

The human eye anomaly aniridia is normally caused by intragenic mutations of PAX6. Several cases of aniridia are, however, associated with chromosomal rearrangements that leave the PAX6 gene intact. We have identified and characterized a novel gene, PAXNEB (C11orf19), downstream (telomeric) of PAX6. Sequence analysis, including interspecies comparisons, show this gene to consist of 10 exons, with an unusually large final intron spanning 134 kb in human and 18 kb in Fugu. This intron is disrupted by each chromosomal rearrangement. The 2-kb PAXNEB transcript, encoding a 424-amino acid protein, is expressed in all cell lines tested. The homologous mouse cDNA is broadly expressed in mouse embryos. PAXNEB is highly conserved from mammals to fish, with some regions of the protein showing conservation to invertebrates, yeast, and plants. The possible role of PAXNEB in aniridia was assessed. Using a transgenic mouse model, we show that the aniridia phenotype of the chromosomal rearrangement cases is not due to the heterozygous loss of PAXNEB function.

Aniridia-associated translocations, DNase hypersensitivity, sequence comparison and transgenic analysis redefine the functional domain of PAX6

The transcription factor PAX6 plays a critical, evolutionarily conserved role in eye, brain and olfactory development. Homozygous loss of PAX6 function affects all expressing tissues and is neonatally lethal; heterozygous null mutations cause aniridia in humans and the Small eye (Sey) phenotype in mice. Several upstream and intragenic PAX6 control elements have been defined, generally through transgenesis. However, aniridia cases with chromosomal rearrangements far downstream of an intact PAX6 gene suggested a requirement for additional cis-acting control for correct gene expression. The likely location of such elements is pinpointed through YAC transgenic studies. A 420 kb yeast artificial chromosome (YAC) clone, extending well beyond the most distant patient breakpoint, was previously shown to rescue homozygous Small eye lethality and correct the heterozygous eye phenotype. We now show that a 310 kb YAC clone, terminating just 5' of the breakpoint, fails to influence the Sey phenotypes. Using evolutionary sequence comparison, DNaseI hypersensitivity analysis and transgenic reporter studies, we have identified a region, >150 kb distal to the major PAX6 promoter P1, containing regulatory elements. Components of this downstream regulatory region drive reporter expression in distinct partial PAX6 patterns, indicating that the functional PAX6 gene domain extends far beyond the transcription unit.

Role of Pax6 in development of the cerebellar system

Post-mitotic neurons generated at the rhombic lip undertake long distance migration to widely dispersed destinations, giving rise to cerebellar granule cells and the precerebellar nuclei. Here we show that Pax6, a key regulator in CNS and eye development, is strongly expressed in rhombic lip and in cells migrating away from it. Development of some structures derived from these cells is severely affected in Pax6-null Small eye (Pax6(Sey)/Pax6(Sey)) embryos. Cell proliferation and initial differentiation seem unaffected, but cell migration and neurite extension are disrupted in mutant embryos. Three of the five precerebellar nuclei fail to form correctly. In the cerebellum the pre-migratory granule cell sub-layer and fissures are absent. Some granule cells are found in ectopic positions in the inferior colliculus which may result from the complete absence of Unc5h3 expression in Pax6(Sey)/Pax6(Sey) granule cells. Our results suggest that Pax6 plays a strong role during hindbrain migration processes and at least part of its activity is mediated through regulation of the netrin receptor Unc5h3.

A cluster of equine granulomatous enteritis cases: the link with aluminium

A cluster of 6 cases of equine granulomatous enteritis is described. Aluminium was demonstrated in the tissues and lesions of these horses and in the intimal bodies of intestinal vessels. The relationship between granulomatous lesions, aluminium, acidity and invading microorganisms, particularly parasites, is presented and discussed.

Combined SSCP/heteroduplex analysis in the screening for PAX6 mutations

We demonstrate the use of combined SSCP and heteroduplex analysis in the detection of PAX6 mutations using non-radioactive silver staining. A panel of aniridia patients was screened by this approach and we show that a greater number of mutations was detected than would have been found by running each technique alone. Six previously unreported aniridia mutations in PAX6 are also described..

A high-resolution integrated physical, cytogenetic, and genetic map of human chromosome 11: distal p13 to proximal p15.1

We describe a detailed physical map of human chromosome 11, extending from the distal part of p13 through the entirety of p14 to proximal p15.1. The primary level of mapping is based on chromosome breakpoints that divide the region into 20 intervals. At higher resolution YACs cover approximately 12 Mb of the region, and in many places overlapping cosmids are ordered in contiguous arrays. The map incorporates 18 known genes, including precise localization of the GTF2H1 gene encoding the 62-kDa subunit of TFIIH. We have also localized four expressed sequences of unknown function. The physical map incorporates genetic markers that allow relationships between physical and genetic distance to be examined, and similarly includes markers from a radiation hybrid map of 11. The cytogenetic location of cosmids has been examined on high-resolution banded chromosomes by fluorescence in situ hybridization, and FLpter values have been determined. The map therefore fully integrates physical, genic, genetic, and cytogenetic information and should provide a robust framework for the rapid and accurate assignment of new markers at a high level of resolution in this region of 11p.

Regional localisation of 19 brain expressed sequence tags to human chromosome 11 using PCR amplification of somatic cell hybrid DNAs

Expressed sequence tags (ESTs) provide an efficient route to the identification of genes involved in normal development and in disease. PCR amplification of somatic cell hybrid DNAs was used to localise 22 brain-derived ESTs to subregions of human chromosome 11. Problems encountered with the standardised PCR conditions were overcome by optimising the annealing temperatures and the use of "touchdown" PCR. Amplification of the correct target sequence allowed the mapping of 19 ESTs, 8 to the short arm and 11 to the long arm of chromosome 11. No definitive localisation could be determined for the three remaining ESTs.

The gene encoding myeloid alpha-3-fucosyl-transferase (FUT4) is located between D1 1S388 and D11S919 on 11q21

The last step in the biosynthesis of Le(x) antigen, the addition of a fucose to precursor polysaccharides, can be catalyzed by different alpha-3-fucosyltransferases. We localized the gene (FUT4) encoding myeloid alpha-3-fucosyltransferase by PCR assay using panels of somatic cell and radiation hybrids which retain different rearrangements of chromosome 11. FUT4 was assigned to chromosome band 11q21 between D11S388 and D11S919.

PAX6 mutations in aniridia

Aniridia is a congenital malformation of the eye, chiefly characterised by iris hypoplasia, which can cause blindness. The PAX6 gene was isolated as a candidate aniridia gene by positional cloning from the smallest region of overlap of aniridia-associated deletions. Subsequently PAX6 intragenic mutations were demonstrated in Smalleye, a mouse mutant which is an animal model for aniridia, and six human aniridia patients. In this paper we describe four additional PAX6 point mutations in aniridia patients, both sporadic and familial. These mutations highlight regions of the gene which are essential for normal PAX6 function. In addition, the frequency at which we have found PAX6 mutations suggests that lesions in PAX6 will account for most cases of aniridia.

Human RAG2, like RAG1, is on chromosome 11 band p13 and therefore not linked to ataxia telangiectasia complementation groups

Ataxia telangiectasia (A-T) is an inherited, recessive, cancer-prone disease with associated immunodeficiency and chromosome abnormalities involving TCR loci. The latter phenomena implicate errors of the enzyme(s) responsible for assembly of antigen receptor genes (recombinase) in disease pathogenesis. Here we report the location of a human recombination activating gene (RAG2), in addition to RAG1, on chromosome 11, band p13, thereby formally demonstrating linkage of these genes in humans and showing that they are not linked to the known locus responsible for the A-T syndrome.

The human BDNF gene maps between FSHB and HVBS1 at the boundary of 11p13-p14

To map in detail the human gene for brain derived neurotrophic factor (BDNF) we have used a PCR-based assay to amplify the gene from somatic cell hybrids containing human chromosome 11 with deletion or translocation breakpoints in the WAGR region. The BDNF gene maps between the FSHB and HVBS1 loci, an interval of approximately 4 Mb at the boundary of 11p13 and 11p14.

The human PAX6 gene is mutated in two patients with aniridia

Aniridia is an inherited ocular disorder of variable expressivity characterized by iris hypoplasia. A candidate aniridia gene, AN, which is the human homologue of the mouse Pax-6 gene, has recently been isolated by positional cloning from the WAGR region of 11p13. Here we describe mutations in this gene in two cases of sporadic aniridia, one detected at the DNA level and one at the RNA level, both of which are predicted to affect protein function. Mutations in Pax-6 have been described previously in Small eye, the proposed mouse model for aniridia. We present new phenotypic evidence for the validity of this mouse model.

Modulation of DNA binding specificity by alternative splicing of the Wilms tumor wt1 gene transcript

The technique of whole-genome polymerase chain reaction was used to study the DNA binding properties of the product of the wt1 gene. The zinc finger region of this gene is alternatively spliced such that the major transcript encodes a protein with three extra amino acids between the third and fourth fingers. The minor form of the protein binds specifically to DNA. It is now shown that the major form of wt1 messenger RNA encodes a protein that binds to DNA with a specificity that differs from that of the minor form. Therefore, alternative splicing within the DNA binding domain of a transcription factor can generate proteins with distinct DNA binding specificities and probably different physiological targets.

Equivalent expression of paternally and maternally inherited WT1 alleles in normal fetal tissue and Wilms' tumours

Observations of non-random maternal 11p allele loss in Wilms' tumour (WT) have implied the possible involvement of an imprinted 11p locus in WT aetiology. A proposed 11p13 Wilms' tumour gene, WT1, has recently been isolated and encodes a zinc finger DNA-binding protein, the 3' untranslated region of which contains a polymorphic dinucleotide repeat (CA repeat) motif. We have exploited this transcribed CA repeat to examine the allelic expression pattern of WT1 and thereby determine whether transcriptional imprinting of this gene occurs. DNA and reverse-transcribed RNA from tumours and normal tissue were subjected to the polymerase chain reaction (PCR) using radiolabelled primers flanking the CA repeat. The gene was seen to be expressed from both of the constitutive alleles in 9-week human fetal kidney, all informative Wilm's tumours and neonatal kidney tissue adjacent to the tumours. In one tumour, known to be heterozygous for a point mutation in zinc finger 2, direct sequencing confirmed that both mutant and wild-type transcripts were being expressed. These results demonstrate that this gene is not subject to transcriptional imprinting in tumours or normal fetal kidney.

Role for the Wilms tumor gene in genital development?

Detailed molecular definition of the WAGR region at chromosome 11p13 has been achieved by chromosome breakpoint analysis and long-range restriction mapping. Here we describe the molecular detection of a cytogenetically invisible 1-megabase deletion in an individual with aniridia, cryptorchidism, and hypospadias but no Wilms tumor (WT). The region of overlap between this deletion and one associated with WT and similar genital anomalies but no aniridia covers a region of 350-400 kilobases, which is coincident with the extent of homozygous deletion detected in tumor tissue from a sporadic WT. A candidate WT gene located within this region has recently been isolated, suggesting nonpenetrance for tumor expression in the first individual. The inclusion within the overlap region of a gene for WT predisposition and a gene for the best-documented WT-associated genitourinary malformations leads us to suggest that both of these anomalies result from a loss-of-function mutation at the same locus. This in turn implies that the WT gene exerts pleiotropic effect on both kidney and genitourinary development, a possibility supported by the observed expression pattern of the WT candidate gene in developing kidney and gonads.

CpG islands surround a DNA segment located between translocation breakpoints associated with genitourinary dysplasia and aniridia

We have isolated a DNA segment absent from all the constitutionally deleted chromosomes 11 of our patients with Wilms tumor. This marker separates two balanced translocations that break in band 11p13: the distal one associated with aniridia (AN2), and the proximal one with genitourinary dysplasia (GUD). The GUD breakpoint maps within the smallest region of overlap (SRO) for the Wilms tumor (WT) gene locus, thus strengthening the previous suggestion of an association between Wilms tumor and other abnormalities of the genitourinary system. The 11p13 translocation breakpoint associated with T-cell acute lymphatic leukemia (T-ALL) is centromeric to the SRO and separated from the WT locus by at least one known gene. This region of the human genome (11p13) is rich in CpG islands that potentially identify genes, some of which may be involved in the various phenotypes associated with the WAGR syndrome. This is consistent with the proposition that the majority of human genes are in G-negative bands.

Analysis of WAGR deletions and related translocations with gene-specific DNA probes, using FACS-selected cell hybrids

We used the fluorescence-activated cell sorter (FACS) to select a series of somatic cell hybrids with deleted or translocated chromosome 11 segregated from its normal homolog. Analysis of these cell hybrids with gene-specific probes and for cell-surface marker expression has allowed us to order the markers and define a smallest region of overlap (SRO) for deletions associated with the WAGR (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation) region of chromosome 11. Two translocation breakpoints in 11p13 (one associated with familial aniridia and one with a sporadic case of congenital renal dysfunction resulting from urethral and ureteral atresia) map within this SRO.

HRAS1-selected chromosome transfer generates markers that colocalize aniridia- and genitourinary dysplasia-associated translocation breakpoints and the Wilms tumor gene within band 11p13

We show that chromosome-mediated gene transfer can provide an enriched source of DNA markers for predetermined, subchromosomal regions of the human genome. Forty-four human DNA recombinants isolated from a HRAS1-selected chromosome-mediated gene transformant map exclusively to chromosome 11, with several sublocalizing to the Wilms tumor region at 11p13. We present a detailed molecular map of the deletion chromosomes 11 from five WAGR (Wilms tumor/aniridia/genitourinary abnormalities/mental retardation) syndrome patients, three of which are at the limits of cytogenetic resolution but shown here to be molecularly distinguishable and overlapping. We can define ten distinct regions of the short arm of chromosome 11, five of which subdivide band 11p13. We also map two independent 11p13 translocation breakpoints to within the smallest region of overlap defined by the WAGR deletions. The first comes from a patient with familial aniridia, and the second from a patient with Potter facies and genitourinary dysplasia. The close similarities in map location and affected cell lineage for Wilms tumor and genitourinary dysplasia suggest that they may be alternative manifestations of mutation at the same locus.

Use of catalase polymorphisms in the study of sporadic aniridia

Catalase is known to map at chromosome 11p13. It is one of the closest known markers to the WAGR locus. Restriction fragment length polymorphisms (RFLP) of the catalase gene may be invaluable for studying rearrangements in somatic tumours, linkage in cases of familial Wilms tumour, and the relationship between sporadic and familial aniridia. We describe a catalase RFLP with two different enzymes and use these polymorphisms to exclude deletion of the catalase gene in patients with sporadic aniridia, including one who is known to have a deletion and another suspected of having a deletion.

Molecular analysis of chromosome 11 deletions in aniridia-Wilms tumor syndrome

We describe five individuals who have constitutional deletions of the short arm of one chromosome 11, including all or part of the band p13. All of these individuals suffer from aniridia; two have had a Wilms tumor removed. We have established lymphoblastoid cell lines from these and in three cases constructed somatic cell hybrids containing the deleted chromosome 11. Analysis of DNA from the cell lines and hybrids with a cloned cDNA probe has shown that the catalase gene is deleted in four of five patients. The catalase locus must be proximal to the Wilms and aniridia-related loci. We have not detected a deletion of the beta-globin or calcitonin genes in any of these individuals; we conclude these genes are likely to be outside the region 11p12-11p15.4. In addition, we have used monoclonal antibodies in fluorescence-activated cell sorting analysis to measure expression in the hybrids of two cell surface markers encoded by genes that map to the short arm of chromosome 11. The genes for both of these are deleted in two individuals but are present in the individual with the smallest deletion.

Control of endometrial prostaglandin output in vitro during the estrous cycle of the guinea-pig: influence of estradiol 17-beta, progesterone, oxytocin and calcium ionophore A23187

Agents influencing the output of prostaglandin F2 alpha (PGF2 alpha) from non-pregnant endometrium were investigated by in vitro incubation, for 5 and 19h, using mid-cycle (day 7), end of cycle (day 15), or ovariectomised guinea-pigs. Estradiol 17-beta (10 micrograms/ml) stimulated PGF2 alpha output 24h after incubation with endometrium (p less than 0.05). This stimulation was greater at mid-cycle. Progesterone (50 ng/ml) inhibited output of PGF2 alpha (p less than 0.05) in mid-cycle, end of cycle and ovariectomised guinea-pig cultures. Oxytocin (1 X 10(-5) u/ml) stimulated the output of PGF2 alpha at the end of the cycle, but not at mid-cycle. However, in the presence of estradiol 17-beta (10 micrograms/ml), oxytocin stimulation of mid-cycle PGF2 alpha output was observed. The calcium ionophore A23187 (5 micrograms/ml) stimulated PGF2 alpha synthesis from mid-cycle and end-of-cycle endometrium, and this stimulation resembled that caused by arachidonic acid (100 micrograms/ml), suggesting an action via substrate mobilisation. Co-culture of endometrium and myometrium did not influence endometrial PGF2 alpha or myometrial 6-oxo-PGF2 output. It is suggested that the steroid hormones act as coarse modulators of endometrial PGF2 alpha output, but more rapid changes may be achieved by oxytocin and agents that mobilise substrate supply, possibly via calcium ion fluctuations.

Prostacyclin and thromboxane A2 in thrombotic thrombocytopenic purpura

A study was conducted to find whether a deficiency in prostacyclin (prostaglandin I2; PGI2) is implicated in the pathogenesis of thrombotic thrombocytopenic purpura. Plasma samples from two patients with the disease before treatment and from 22 healthy controls were therefore assayed for concentrations of 6-oxo-PGF1 alpha and thromboxane B2, the stable metabolites of PGI2 and thromboxane A2, respectively. Neither of the patients responded to treatment, which in one case included an infusion of PGI2. Both patients had normal concentrations of 6-oxo-PGF1 alpha and thromboxane B2, thus implying that circulating amounts of PGI2 and thromboxane A2 were also normal. These findings suggest that 6-oxo-PGF1 alpha may be detectable in normal amounts in thrombotic thrombocytopenic purpura and that the condition need not be associated with a high concentration of thromboxane A2.