Chondrodysplasia with multiple dislocations: comprehensive study of a series of 30 cases

The group of chondrodysplasia with multiple dislocations includes several entities, characterized by short stature, dislocation of large joints, hand and/or vertebral anomalies. Other features, such as epiphyseal or metaphyseal changes, cleft palate, intellectual disability are also often part of the phenotype. In addition, several conditions with overlapping features are related to this group and broaden the spectrum. The majority of these disorders have been linked to pathogenic variants in genes encoding proteins implicated in the synthesis or sulfation of proteoglycans (PG). In a series of 30 patients with multiple dislocations, we have performed exome sequencing and subsequent targeted analysis of 15 genes, implicated in chondrodysplasia with multiple dislocations, and related conditions. We have identified causative pathogenic variants in 60% of patients (18/30); when a clinical diagnosis was suspected, this was molecularly confirmed in 53% of cases. Forty percent of patients remain without molecular etiology. Pathogenic variants in genes implicated in PG synthesis are of major importance in chondrodysplasia with multiple dislocations and related conditions. The combination of hand features, growth failure severity, radiological aspects of long bones and of vertebrae allowed discrimination among the different conditions. We propose key diagnostic clues to the clinician.

Identification of novel striatal genes by expression profiling in adult mouse brain

Large-scale transcriptome analysis in the brain is a powerful approach to identify novel genes of potential interest toward understanding cerebral organization and function. We utilized the microarray technology to measure expression levels of about 24,000 genes and expressed sequence tags in mouse hippocampus, frontal cortex and striatum. Using expression profile obtained from whole brain as a reference, we categorized the genes into groups of genes either enriched in, or restricted to, one of the three areas of interest. We found enriched genes for each target area. Further, we identified 14 genes in the category of genes restricted to the striatum, among which were the orphan G protein-coupled receptor GPR88 and retinoic acid receptor-beta. These two genes were already reported to be selectively expressed in the striatum, thus validating our experimental approach. We selected 6 striatal-restricted genes, as well as 10 striatal-enriched candidates, that were previously undescribed. We analyzed their expression by in situ hybridization analysis in the brain, and quantitative RT-PCR in both brain and peripheral organs. Two of these unknown genes displayed a notable expression pattern. The striatal-restricted gene H3076B11 shows uniform expression throughout and uniquely in the striatum, representing a genuine striatal marker. The striatal-enriched gene 4833421E05Rik is preferentially expressed in the rostral striatum, and is also abundant in kidney, liver and lung. These two genes may contribute to some of the many striatal-controlled behaviors, including initiation of movement, habit formation, or reward and motivation.

From the molecular biology of prolactin and its receptor to the lessons learned from knockout mice models

Prolactin (PRL), a polypeptide hormone secreted mainly by the pituitary and, to a lesser extent, by peripheral tissues, affects more physiological processes than all other pituitary hormones combined since it is involved in > 300 separate functions in vertebrates. Its main actions are related to lactation and reproduction. The initial step of PRL action is the binding to a specific membrane receptor, the PRLR, which belongs to the class 1 cytokine receptor superfamily. PRL-binding sites have been identified in a number of tissues and cell types in adult animals. Signal transduction by this receptor is mediated, at least in part, by two families of signaling molecules: Janus tyrosine kinases and signal transducers and activators of transcription (STATs). Disruption of the PRLR gene has provided a new mouse model with which to identify actions directly associated with PRL or any other PRLR ligands, such as placental lactogens. To date, several different phenotypes have been analyzed and are briefly described in this review. Coupled with the SAGE technique, this PRLR knockout model is being used to qualitatively and quantitatively evaluate the expression pattern of hepatic genes in two physiological situations: transcriptomes corresponding to livers from both wild type and PRLR KO mice are being compared, and following statistical analyses, candidate genes presenting a differential profile will be further characterized. Such a new approach will undoubtedly open future avenues of research for PRL targets. To date, no pathology linked to any mutation in the genes encoding PRL or its receptor have been identified. The development of genetic models provides new opportunities to understand how PRL can participate to the development of pathologies throughout life, as for example the initiation and progression of breast cancer.

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Prolactin (PRL) and its receptor: actions, signal transduction pathways and phenotypes observed in PRL receptor knockout mice

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Prolactin: a hormone at the crossroads of neuroimmunoendocrinology

Prolactin (PRL), secreted by the pituitary, decidua, and lymphoid cells, has been shown to have a regulatory role in reproduction, immune function, and cell growth in mammals. The effects of PRL are mediated by a membrane-bound receptor that is a member of the superfamily of cytokine receptors. Formation of a trimer, consisting of one molecule of ligand and two molecules of receptor, appears to be a necessary prerequisite for biological activity. The function of these receptors is mediated, at least in part, by two families of signaling molecules: Janus tyrosine kinases (JAKs) and signal transducers and activators of transcription (STATs). To study these receptors, we have used two approaches: mutational analysis of their cytoplasmic domains coupled with functional tests and inactivation (knockout) of the receptor gene by homologous recombination in mice. We have produced mice by gene targeting in embryonic stem cells carrying a germline null mutation of the prolactin receptor gene. Heterozygous (+/-) females show almost complete failure to lactate, following their first, but not subsequent pregnancies. Homozygous (-/-) females are infertile as a result of multiple reproductive abnormalities, including ovulation of premiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Half of the homozygous males are infertile or show reduced fertility. In view of the wide-spread distribution of PRL receptors, other phenotypes including those on the immune system, are currently being evaluated in -/- animals. This study establishes the prolactin receptor as a key regulator of mammalian reproduction and provides the first total ablation model to further study the role of the prolactin receptor and its ligands.

Suppression subtractive hybridization (SSH) identifies prolactin stimulation of p38 MAP kinase gene expression in Nb2 T lymphoma cells: molecular cloning of rat p38 MAP kinase

Suppression Subtractive Hybridization (SSH) has been used to compare rat Nb2 cells treated with prolactin for 1 hour with untreated cells. This new method for identifying differentially expressed genes showed that the mRNAs for at least three genes were elevated by such treatment, including a p38 mitogen activated protein (MAP) kinase. The p38 MAP kinase was cloned and the full length cDNA sequence was determined.

In vivo study of prolactin (PRL) intracellular signalling during lactogenesis in the rat: JAK/STAT pathway is activated by PRL in the mammary gland but not in the liver

The rat prolactin receptor (PRL-R) exists in two forms, which differ in the length of the cytoplasmic domains, tissue distribution, and biological activity. The short form predominates in liver while the long form is prevalent in mammary gland. We have compared activation by PRL of the JAK2-STAT pathway (protein tyrosine phosphorylation and STAT5 activation) in mammary gland and liver in an in vivo rat model of induction of lactogenesis by PRL injections, and we have studied the relative proportion of both forms of the receptor in these tissues by reverse transcription-polymerase chain reaction. Rats were ovario-hysterectomized on Day 19 of pregnancy, treated with bromocriptine, subsequently injected with 250 micrograms ovine PRL i.p. on Day 20, and killed 0-12 h after. Western blots of solubilized mammary gland and liver membranes immunoprecipitated with anti-PRL-R or anti-JAK2 antibodies showed that the PRL-R is constitutively associated with JAK2 and that the long form of the PRL-R is present in both tissues, while the short form was detected only in liver. Phosphorylated proteins corresponding to the long form of PRL-R and JAK2 appeared 15-60 min after ovine PRL injection in mammary extracts but not in liver. At these same times, an electrophoretic mobility shift assay, using a rat beta-casein probe specific for STAT5 binding, showed activated STAT5 in mammary gland cytosol and nuclear extracts. In the liver, low levels of activated STAT5 were detected in non-treated animals, which were not modified by PRL. Quantitative RT-PCR of liver and mammary PRL-R mRNA showed that the amount of the long form of PRL-R mRNA is roughly comparable in both tissues, while the short form is predominant in liver and in a minority in mammary tissue. Both forms were down-regulated by PRL only in mammary glands. Thus, during lactogenesis, mammary tissue responds to PRL by activation of JAK2 and STAT5, while the liver does not respond to PRL in spite of the presence of PRL-R associated with JAK2 and pre-existing activated STAT5. Thus, liver tissue may lack a critical component for activation of the PRL pathway, or the large quantities of the short form of the PRL-R may associate with the long form to constitute inactive heterodimers.

Regulation of prolactin receptor mRNA expression in peripheral lymphocytes in rats in response to changes in serum concentrations of prolactin

In the present study we have evaluated the absolute number of the two forms of prolactin (PRL) receptor mRNA in rat peripheral blood lymphocytes and the modulation of receptor mRNA induced by changes in serum levels of endogenous PRL or by administration of ovine PRL. Lymphocytes expressed low levels of both forms of PRL receptor transcripts. Repeated treatments with ovine PRL significantly reduced levels of mRNA encoding the long form PRL receptor, whereas expression was markedly increased by repeated doses of bromocriptine. In contrast, the mRNA level of short form PRL receptor was unchanged by both treatments. The expression of long form transcripts was also markedly decreased in lymphocytes from pituitary-grafted rats. Therefore it appears that in rat peripheral lymphocytes PRL has a negative effect on the expression of its own receptor.