100. IN VIVO DIFFERENTIATION OF HUMAN EMBRYONIC STEM CELLS TO UTERINE TISSUE

The endometrium undergoes cyclic regeneration. This regeneration has been attributed to adult stem progenitor cells and developmental mechanisms [1, 2]. A better understanding of human endometrial development may shed light on the mechanisms involved in endometrial regeneration and on early origins of adult endometrial disease. The lack of human fetal endometrial tissue has impeded research in early human endometrial development. We hypothesized that directed differentiation of human embryonic stem cells (hESC) to human endometrial tissue by neonatal mouse uterine mesenchyme represents a novel system to study early development of human endometrium. Recent studies have shown that the neonatal mouse uterine mesenchyme is extremely inductive and undergoes reciprocal signalling with human endometrial epithelial cells [3]. Our aim is to establish a xenograft tissue recombination protocol based on a model for human prostate tissue differentiation using hESC [4]. Our method involved formation of embryoid body (EB) with GFP labelled hESC (ENVY) [5] for recombination with 2x0.5mm pieces of epithelial-free uterine mesenchyme from postnatal day 1 mice. Upon fusion in culture, the recombinant tissue is grafted under the kidney capsule of NOD/SCID mice for 4-12 weeks and monitored by in-vivo imaging. Immunohistochemical analysis of recombinant grafts 4 weeks post transplantation (n=4) revealed immature CK8+CK18+Hoxa10+ human epithelial cells surrounded by mouse mesenchymal cells suggesting differentiation of hESC to epithelial cells possibly of endometrial lineage. The ER+PR+SMA+Hoxa10+ mouse mesenchymal cells surrounding human glands differentiated into SMA+ cells possibly via reciprocal signalling from human epithelial cells. At 8 weeks, we found several CK18+/Hoxa10+ human glands co-expressing CA125. These glands are supported by Hoxa10+ human stromal cells. Further experiments are underway to induce the expression of ER and PR in Hoxa10+ epithelial cells which will be crucial in revealing their endometrial lineage.

What causes paramyotonia in the United Kingdom? Common and new SCN4A mutations revealed

OBJECTIVE

To study the clinical and genetic features in a large cohort of UK patients with sodium channel paramyotonia congenita.

METHODS

We conducted a UK-wide clinical and molecular genetic study of patients presenting with a phenotype suggestive of paramyotonia congenita.

RESULTS

We identified 42 affected individuals (28 kindreds). All cases met our core criteria for a clinical diagnosis of paramyotonia congenita. Seventy-five percent of patients (32 patients/20 kindreds) had SCN4A mutations. Twenty-nine subjects from 18 kindreds had exon 22 and 24 mutations, confirming these exons to be hot spots. Unexpectedly, 3 of these subjects harbored mutations previously described with potassium-aggravated myotonia (G1306A, G1306E). We identified two new mutations (R1448L and L1436P). Ten cases (8 kindreds) without mutations exhibited paramyotonia congenita with prominent pain and weakness.

CONCLUSIONS

This study identifies two new mutations, confirms SCN4A as a common cause of paramyotonia congenita in the UK, and suggests further allelic and possibly genetic heterogeneity.

Supracondylar fractures of the humerus associated with ipsilateral forearm fractures in children: a report of forty-seven cases

Supracondylar fractures of the humerus associated with ipsilateral forearm fractures are uncommon and treatment recommendations are controversial. The purpose of this study was to determine whether pin fixation of both fracture components, humerus and forearm, would improve the outcome. In a two-center trial, 884 children sustaining supracondylar fractures of the humerus were retrospectively reviewed, and 47 (5.3%) showed associated ipsilateral forearm fractures. Of those, 29 underwent Kirschner-wire fixation of the forearm fracture, and 18 of the forearm fractures were treated with casting alone. Three of the 18 forearm fractures with casting alone reangulated. There were no reangulations in the patients who had pin fixation of their fractures. There were no complications due to pin fixation in the humerus or the forearm. In unstable supracondylar humerus and forearm fractures, stabilization with pin fixation to prevent reangulation should be considered.

Cardiac septal and valvular dysmorphogenesis in mice heterozygous for mutations in the homeobox gene Nkx2-5

Heterozygous mutations in the cardiac homeobox gene, NKX2-5, underlie familial cases of atrial septal defect (ASD) with severe atrioventricular conduction block. In this study, mice heterozygous for Nkx2-5-null alleles were assessed for analogous defects. Although ASD occurred only rarely, atrial septal dysmorphogenesis was evident as increased frequencies of patent foramen ovale and septal aneurysm, and decreased length of the septum primum flap valve. These parameters were compounded by genetic background effects, and in the 129/Sv strain, septal dysmorphogenesis bordered on ASD in 17% of Nkx2-5 heterozygotes. In a proportion of neonatal heterozygotes, as well as in adults with ASD, we found that the size of the foramen ovale was significantly enlarged and altered in shape, potentially exposing the normally thin septum primum to excessive hemodynamic forces. Therefore, defective morphogenesis of the septum secundum may be one contributing factor in the generation of patent foramen ovale, septal aneurysm, and certain ASDs. Mild prolongation of P-R interval in females and an increased frequency of stenotic bicuspid aortic valves were also features of the Nkx2-5 heterozygous phenotype. Our data demonstrate that the complex effects of Nkx2-5 haploinsufficiency in mice are weaker but convergent with those in humans. As in the mouse, the phenotype of human NKX2-5 mutations may be modulated by interacting alleles.

A randomized double blind-cross over trial of soya protein for the treatment of cyclical breast pain

Twenty patients with cyclical breast pain were enrolled in a double-blind cross-over trial in which either a soy protein drink or a flavoured cow's milk was taken orally each day for 3 months before crossing over to the alternate drink for a further 3 months. Records of pain scores were taken throughout the study. Blood was also taken before and after 3 and 6 months for the measurement of phytoestrogents to assess compliance. Two women withdrew from the study at the outset leaving 18 evaluable patients who completed the study. Of these 10 (56%) felt that soy protein improved breast pain (two of whom received soy as first treatment) and two (11%) felt that cow's milk alleviated symptoms (one receiving this as first preparation) and the remaining six (33%) experienced no relief of pain with either dietary preparation. Blood levels of diadzein and genistein were elevated after the ingestion of soy protein in only 13 patients (seven of whom felt that soy improved their breast pain); in the remaining five patients (three of whom suggested that soy protein improved breast pain) phytoestrogen levels were no higher than pretreatment values. Although the ingestion of soy protein may be associated with relief of breast pain, these results illustrate the problem of non-specific effects in studies of mastalgia in that 1) cow's milk also relieved breast pain in some patients and 2) that the benefits of soy protein were not always associated with evidence of elevated circulating levels of phyto-estrogens, indicating the difficulty of compliance in dietary intervention studies using soy foods.

Identification of four loci isolated from two Streptococcus thermophilus phage genomes responsible for mediating bacteriophage resistance

Sequence data derived from the Streptococcus thermophilus phages phiO1205 and phi7201 indicated that each of these phages contains a distinct DNA region dedicated to replication. Southern blotting experiments showed that phages infecting S. thermophilus may be divided into at least two groups, each containing the presumptive replication functions of either φO1205 (group I) or φ7201 (group II). Specific regions from the putative replication module of each of the two phages were examined for their ability to provide phage resistance.

Characterisation of Streptococcus thermophilus CNRZ1205 and its cured and re-lysogenised derivatives

Streptococcus thermophilus CNRZ1205 is the lysogenic host for the temperate phage phi O1205. A derivative of CNRZ1205 was isolated which was cured of phi O1205 and this strain was used to construct a re-lysogenised derivative. Pulse field gel electrophoresis and sequencing of the attachment site regions confirmed that excision and re-integration of the phage was a site-specific event. Interestingly, cells from the cured, as well as its re-lysogenised derivative, were found to have a very long chain length.

Identification and characterization of a lysis module present in a large proportion of bacteriophages infecting Streptococcus thermophilus

A lysis module encoded by the temperate bacteriophage phiO1205 was identified. This lysis module contains a lysin gene, designated lyt51, and two putative holin-encoding genes, designated lyt49 and lyt50. lyt51 encodes a lytic enzyme specifically directed against streptococcal cell walls. Similar to other phage-encoded lysins, Lyt51 appears to have a modular design in which the N-terminal portion corresponds to its enzymatic activity while the C-terminal region is responsible for its substrate binding specificity. The two putative holin-encoding genes, lyt49 and lyt50, located immediately upstream of lyt51, were identified on the basis of their homology to other identified holin-encoding genes. Expression of lyt49 or lyt50 in Escherichia coli was shown to cause cell death and leakage of the intracellular enzyme isocitrate dehydrogenase into the growth medium without apparent lysis of the cells. Southern blotting experiments demonstrated that at least one of the three components of the identified lysis module is present in all members of a large collection of bacteriophages, indicating that components of this lysis module are widespread among bacteriophages infecting Streptococcus thermophilus.

DAN is a secreted glycoprotein related to Xenopus cerberus

We report that DAN, a potential cell cycle regulator and tumour suppressor, is a secreted glycoprotein related to Xenopus cerberus. DAN, cerberus, its mouse relative Cer-1/cer-l/Cerberus-like/Cerr1, and the recently described factor DRM/Gremlin, appear to be members of the cystine knot superfamily, which includes TGFbetas and BMPs. Like cerberus and mCer-1, DAN-induced cement glands as well as markers of anterior neural tissue and endoderm in Xenopus animal cap assays, features of BMP signalling blockade. During mouse embryogenesis, Dan was expressed from E8.5 in cranial mesenchyme and somites, then later in limb and facial mesenchyme. The pattern in somites was highly dynamic, with transcripts initially localized to the caudal half of the nascent epithelial somite, then, after maturation, to sclerotomal cells adjacent to the neural tube. Dan was also expressed in the developing myotome. The expression domains include sites in which BMP inhibition is known to be important for development. Thus, DAN appears to be a secreted factor belonging to the cystine knot superfamily, and one of a growing number of antagonists acting to modulate BMP signalling during development.

Murine cerberus homologue mCer-1: a candidate anterior patterning molecule

Xenopus cerberus (Xcer) is a cytokine expressed in anterior mesendoderm overlapping and surrounding Spemann's gastrula organiser. When misexpressed in blastomeres, Xcer can induce ectopic heads with well-defined brain, cement gland, olfactory placodes, cyclopic eye, and occasionally liver and heart. We report here the identification of mCer-1, a murine gene related to cerberus. Both mCer-1 and Xcer appear to belong to the cystine knot superfamily, which includes TGF beta s and BMPs. In Xenopus animal cap assays, mCer-1 and Xcer induced cement glands and markers of anterior neural tissue and endoderm, characteristic of BMP inhibition. Furthermore, both antagonised the ventrolateral mesoderm-inducing activity of coexpressed BMP4. In mouse embryos, mCer-1 was expressed at early gastrulation in a stripe of primitive endoderm along the future anterior side of the egg cylinder, a region essential for anterior patterning. A second phase of expression was detected in anterior embryonic mesendoderm, and by late-streak stages most of the anterior half of the embryo was positive, except for the node and cardiac progenitors. Expression was later seen in the cranial portion of the two most-recently formed somites and in two stripes within presomitic mesoderm. In embryos lacking Otx2, a homeogene with a demonstrated role in anterior patterning, mCer-1 was still expressed in an anterior zone, although often abnormally. The data suggest that mCer-1 shares structural, functional, and expression characteristics with Xcer and may participate in patterning the anterior of the embryo and nascent somite region, in part, through a BMP-inhibitory mechanism.

Sequence analysis and characterization of phi O1205, a temperate bacteriophage infecting Streptococcus thermophilus CNRZ1205

The complete nucleotide sequence of phi O1205, a temperate bacteriophage infecting Streptococcus thermophilus strain CNRZ1205, was determined. The phage genome has a unit length of 43,075 bp and appears to be packaged by the so-called headful mechanism. The genomic organization and structure of phi O1205 resemble those of several temperate lactococcal phages that display a life-cycle-specific organization, where ORFs believed to be involved in the lysogenic life-cycle are clustered and arranged in an orientation opposite to the ORFs supposedly involved in the lytic life-cycle. Database searches revealed putative functions for several identified ORFs and further indicated that phi O1205 is genetically related to a particular group of lactococcal phages. Three genes encoding the major structural proteins were identified on the phi O1205 genome. The phage attachment site attP, the bacterial attachment site attB, and the two phage/chromosome junctions attL and attR were identified and found to contain a 40 bp common core sequence.

Two groups of bacteriophages infecting Streptococcus thermophilus can be distinguished on the basis of mode of packaging and genetic determinants for major structural proteins

A comparative study of 30 phages of Streptococcus thermophilus was performed based on DNA restriction profiles, DNA homology, structural proteins, packaging mechanisms, and host range data. All phages exhibited distinct DNA restriction profiles, with some phages displaying similarly sized restriction fragments. DNA homology was shown to be present among all 30 phages. The phages could be divided into two groups on the basis of their packaging mechanism as was derived from the appearance of submolar DNA fragments in restriction enzyme digests and the presence (cos-containing phages) or absence (pac-containing phages) of cohesive genomic extremities. Interestingly, the 19 identified cos-containing phages possessed two major structural proteins (32 and 26 kDa) in contrast to the remaining 11 pac-containing phages, which possessed three major structural proteins (41, 25, and 13 kDa). Southern hybridization demonstrated that all pac-containing phages tested contain homologs of the genes encoding the three major structural proteins of the pac-containing phage O1205, whereas all cos-containing phages tested exhibit homology to the gene specifying one of the structural components of the cos-containing phage phi 7201. Fifty-seven percent of the phages (both cos and pac containing) possessed the previously identified 2.2-kb EcoRI fragment of the temperate S. thermophilus phage Sfi18 (H. Brüssow, A. Probst, M. Frémont, and J. Sidoti, Virology 200:854-857, 1994). No obvious correlation was detected between grouping based on packaging mechanism and host range data obtained with 39 industrial S. thermophilus strains.

Autophosphorylation induces autoactivation and a decrease in the Src homology 2 domain accessibility of the Lyn protein kinase

Lyn is a member of the Src family of protein-tyrosine kinases that can readily undergo autophosphorylation in vitro. The site of autophosphorylation is Tyr397 which corresponds to the consensus autophosphorylation site of other Src family tyrosine kinases. The rate of autophosphorylation is concentration-dependent, indicating that the reaction follows an intermolecular mechanism. Autophosphorylation results in a 17-fold increase in protein-tyrosine kinase activity. Kinetic analysis demonstrates that phosphorylation of a substrate peptide by Lyn following autophosphorylation occurs with a 63-fold decrease in Km but no significant change in Vmax, suggesting that autophosphorylation relieves the conformational constraint that prevents binding of the substrate peptide to the active site of the kinase. Using a phosphotyrosine-containing peptide (pYEEI) that has previously been shown to bind to the Src homology 2 (SH2) domain of Src family tyrosine kinases with high affinity, we found that autophosphorylation results in a significant decrease in accessibility of the Lyn SH2 domain, indicating that conformational changes in the protein kinase domain induced by autophosphorylation can be propagated to the SH2 domain. Our study suggests that autophosphorylation plays an important role in regulating Lyn by modulating both its kinase activity and its interaction with other phosphotyrosine-containing molecules.

Identification of a duplication of the mouse Lyn gene

The Lyn gene encodes a PTK that is believed to participate in the transduction of signals from a variety of cell membrane receptors. Here we report the genomic organisation of the mouse Lyn gene and show that, while the promoter and exons 11-13 are present in single copy, sequences corresponding to the first coding exon are duplicated and this duplication extends into intron 10. Two sets of genomic clones representing the duplicated regions have been isolated and characterised. Nucleotide sequence analysis of these clones has revealed minimal sequence divergence between the two, suggesting that the duplication is a recent event. This is supported by Southern blot analysis of DNA from other mammalian species showing that the duplication is confined to the mouse. Aside from the duplicated sequences, the overall structure of the mouse Lyn gene is similar to that of other Src family members. These data suggest that the process of duplication which generated the Src family of PTK is an ongoing process and provide an insight into the molecular evolution of this group of genes.