American marsupials chromosomes: Why study them?

Marsupials, one of the three main groups of mammals, are only found in Australia and in the American continent. Studies performed in Australian marsupials have demonstrated the great potential provided by the group for the understanding of basic genetic mechanisms and chromosome evolution in mammals. Genetic studies in American marsupials are relatively scarce and cytogenetic data of most species are restricted to karyotype descriptions, usually without banding patterns. Nevertheless, the first marsupial genome sequenced was that of Monodelphis domestica, a South American species. The knowledge about mammalian genome evolution and function that resulted from studies on M. domestica is in sharp contrast with the lack of genetic data on most American marsupial species. Here, we present an overview of the chromosome studies performed in marsupials with emphasis on the South American species

A Methodological Framework for the Reconstruction of Contiguous Regions of Ancestral Genomes and Its Application to Mammalian Genomes

The reconstruction of ancestral genome architectures and gene orders from homologies between extant species is a long-standing problem, considered by both cytogeneticists and bioinformaticians. A comparison of the two approaches was recently investigated and discussed in a series of papers, sometimes with diverging points of view regarding the performance of these two approaches. We describe a general methodological framework for reconstructing ancestral genome segments from conserved syntenies in extant genomes. We show that this problem, from a computational point of view, is naturally related to physical mapping of chromosomes and benefits from using combinatorial tools developed in this scope. We develop this framework into a new reconstruction method considering conserved gene clusters with similar gene content, mimicking principles used in most cytogenetic studies, although on a different kind of data. We implement and apply it to datasets of mammalian genomes. We perform intensive theoretical and experimental comparisons with other bioinformatics methods for ancestral genome segments reconstruction. We show that the method that we propose is stable and reliable: it gives convergent results using several kinds of data at different levels of resolution, and all predicted ancestral regions are well supported. The results come eventually very close to cytogenetics studies. It suggests that the comparison of methods for ancestral genome reconstruction should include the algorithmic aspects of the methods as well as the disciplinary differences in data aquisition

Characteristics Of Growth Hormone Binding To Liver Microsomes Of Pregnant Women

Specific binding of hGH to liver microsomes of nonpregnant women and men is low, usually 10% of less in RRA. In pregnant women, however, we found that this binding is 10 times higher. The binding reaction shared the properties common to receptor systems: time, temperature and cation dependence, saturability and reversibility. hGH specific binding without cations was 10 times lower. The cross-reactions of hPRL and human placental lactogen with hGH were 0.49 ± 0.16% and 0.10 ± 0.05%, respectively. 125I-IiPRL and 125I-human placental lactogen binding to microsomes of two controls and two pregnant women were very low and poorly reproducible. The Scatchard analysis revealed two hGH binding sites, one with an association constant (KA) of 2.7 ± 0.1 × 1010 M-1, and the other with a KA of 1.5 ± 0.1 × 109 M-1. In one nonpregnant woman, we found a single hGH binding site with a KA of 1.5 × 109 M-1, confirming results previously reported in the literature. A HGH RRA was set up with microsomes of pregnant women. Acromegalic sera produced curves parallel to the hGH standard and pituitary dwarf serum had no 125I-hGH displacing activity. Sera of pregnant women produced curves divergent to the hGH standard and showed a 125I-hGH displacing activity 20 to 40 times higher than could be predicted by hGH levels determined by RIA. Cord sera and sera from puerperal women had similar hGH levels as determined by either RRA or RIA (r = 0.93, P < 0.001, slope = 0.85, n = 25). Our results show the existence of specific GH receptors and serum factor(s) with high 125I-hGH displacing activity from these receptors in pregnancy. These findings must be related to several metabolic changes of pregnancy, such as glucose intolerance, hyperinsulinemia, increased lipolysis, and ketogenesis.73234835

Konverteringen og Rentefoden.

Specific binding of hGH to liver microsomes of nonpregnant women and men is low, usually 10% of less in RRA. In pregnant women, however, we found that this binding is 10 times higher. The binding reaction shared the properties common to receptor systems: time, temperature and cation dependence, saturability and reversibility. hGH specific binding without cations was 10 times lower. The cross-reactions of hPRL and human placental lactogen with hGH were 0.49 +/- 0.16% and 0.10 +/- 0.05%, respectively. I-125-hPRL and I-125-human placental lactogen binding to microsomes of two controls and two pregnant women were very low and poorly reproducible. The Scatchard analysis revealed two hGH binding sites, one with an association constant (K(A)) of 2.7 +/- 0.1 x 10(10) M-1, and the other with a K(A) of 1.5 +/- 0.1 x 10(9) M-1. In one nonpregnant woman, we found a single hGH binding site with a K(A) of 1.5 x 10(9) M-1, confirming results previously reported in the literature. A hGH RRA was set up with microsomes of pregnant women. Acromegalic sera produced curves parallel to the hGH standard and pituitary dwarf serum had no I-125-hGH displacing activity. Sera of pregnant women produced curves divergent to the hGH standard and showed a I-125-hGH displacing activity 20 to 40 times higher than could be predicted by hGH levels determined by RIA. Cord sera and sera from puerperal women had similar hGH levels as determined by either RRA or RIA (r = 0.93, P < 0.001, slope = 0.85, n = 25). Our results show the existence of specific GH receptors and serum factor(s) with high I-125-hGH displacing activity from these receptors in pregnancy. These findings must be related to several metabolic changes of pregnancy, such as glucose intolerance, hyperinsulinemia, increased lipolysis, and ketogenesis

Dental developmental abnormalities in a patient with subtelomeric 7q36 deletion syndrome may confirm a novel role for the SHH gene

Studies in mice demonstrated that the Shh gene is crucial for normal development of both incisors and molars, causing a severe retardation in tooth growth, which leads to abnormal placement of the tooth in the jaw and disrupted tooth morphogenesis. In humans the SHH gene is located on chromosome 7q36. Defects in its protein or signaling pathway may cause holoprosencephaly spectrum, a disorder in which the developing forebrain fails to correctly separate into right and left hemispheres and that can be manifested in microforms such as single maxillary central incisor. A novel role for this gene in the developing human primary dentition was recently demonstrated. We report a 12-year old boy with a de novo 7q36.1-qter deletion characterized by high-resolution karyotyping, oligonucleotide aCGH and FISH. His phenotype includes intellectual disability, non-verbal communication, hypospadia, partial sacral agenesis and absence of coccyx, which are distinctive features of the syndrome and mainly correlated with the MNX1, HTR5A and EN2 genes. No microforms of holoprosencephaly spectrum were observed; but the patient had diastema and dental developmental abnormalities, such as conical, asymmetric and tapered inferior central incisors. The dental anomalies are reported herein for the first time in subtelomeric 7q36 deletion syndrome and may confirm clinically a novel role for the SHH gene in dental development.FAPESP (2009/00898-1