Gene polymorphisms as clinical tools in chronic glomerulopathies: a prospective study.

BACKGROUND/AIMS: Studies have proposed various polymorphisms of genes implicated in the physiopathology of chronic kidney disease as risk factors of progression and potential clinical tools. We sought to validate and simultaneously compare their predictive value in a prospective cohort of chronic glomerulopathies receiving recommended antihypertensive and antiproteinuric therapies. METHODS: Using PubMed, we identified 9 polymorphisms previously associated with progression. These were mostly of the renin-angiotensin-aldosterone and inflammation pathways: MCP-1 A2518G, TGF-ß1 T869C and C-509T, ACE I/D, AGT M235T, AT1R A1166C, TSC-22 A-396G, eNOS 4b/a and CYP11ß2 C-344T. We hypothesized that their determination would identify individuals at higher risk of progression. RESULTS: We recruited 93 predominantly male and Caucasian patients with a mean age of 63 and baseline eGFR of 33 ml/min/1.73 m(2) followed prospectively over a median of 36 months. 61% of patients had diabetic nephropathy, almost all received RAA blockade (90%) and none immunosuppressive therapy. The average blood pressure during follow-up was 140/72 mm Hg, the urinary protein to creatinine ratio 0.15 g/mmol and the rate of renal function decline -3.2 ± 4.1 ml/min/1.73 m(2)/year. Proteinuria and blood pressure strongly predicted progression. However, under recommended therapy, none of the proposed polymorphisms predicted renal function decline. In addition, none showed simple or partial correlations with the severity of proteinuria or blood pressure. Finally, summation variable of risk polymorphisms did not predict progression. CONCLUSION: This study does not validate the use of these 9 polymorphisms as individual clinical tools in patients with chronic glomerulopathies on recommended antihypertensive and antiproteinuric therapies.

Genome-wide interrogation of Mammalian stem cell fate determinants by nested chromosome deletions.

Understanding the function of important DNA elements in mammalian stem cell genomes would be enhanced by the availability of deletion collections in which segmental haploidies are precisely characterized. Using a modified Cre-loxP-based system, we now report the creation and characterization of a collection of ∼1,300 independent embryonic stem cell (ESC) clones enriched for nested chromosomal deletions. Mapping experiments indicate that this collection spans over 25% of the mouse genome with good representative coverage of protein-coding genes, regulatory RNAs, and other non-coding sequences. This collection of clones was screened for in vitro defects in differentiation of ESC into embryoid bodies (EB). Several putative novel haploinsufficient regions, critical for EB development, were identified. Functional characterization of one of these regions, through BAC complementation, identified the ribosomal gene Rps14 as a novel haploinsufficient determinant of embryoid body formation. This new library of chromosomal deletions in ESC (DelES: http://bioinfo.iric.ca/deles) will serve as a unique resource for elucidation of novel protein-coding and non-coding regulators of ESC activity.

Platelets play an essential role in separating the blood and lymphatic vasculatures during embryonic angiogenesis.

RATIONALE: Several mutations that impair the development of blood lineages in the mouse also impair the formation of the lymphatic vasculature and its separation from the blood vasculature. However, the basis for these defects has remained unknown because the mutations characterized affect more than one blood lineage. OBJECTIVE: We tested the hypothesis that megakaryocytes/platelets are required for the formation of the lymphatic vasculature and its separation from the blood vascular system. METHODS AND RESULTS: We characterized the vascular patterning defects of mice deficient for the homeodomain transcription factor Meis1 (myeloid ecotropic viral integration site 1), which completely lack megakaryocyte/platelets. Meis1 null embryos fail to separate the blood and lymphatic vasculature, showing blood-filled primary lymphatic sacs and superficial lymphatic vessels. To test the involvement of megakaryocytes/platelets in this phenotype, we generated megakaryocyte/platelet-specific deficient mice by targeted lineage ablation, without affecting other blood lineages. This model reproduces the lymphatic/blood vasculature separation defects observed in Meis1 mutants. A similar phenotype was induced by antibody-mediated ablation of circulating platelets in wild type mice. Strong association of platelets with vascular endothelium at regions of contact between lymphatic sacs and veins confirmed a direct role of platelets in the separation of the 2 vasculatures. CONCLUSIONS: In addition to their known protective function in the response accidental vascular injury, platelets are also required during embryonic lymphangiogenesis for the separation of the nascent lymphatic vasculature from blood vessels.

The homeodomain protein Meis1 is essential for definitive hematopoiesis and vascular patterning in the mouse embryo.

Homeodomain proteins of the Meis subfamily are expressed dynamically in several organs during embryogenesis and exert potent regulatory activity through their interaction with Hox proteins and other transcription factors. Here we show that Meis1 is expressed in the hematopoietic stem cell (HSC) compartment in the fetal liver, and in the primary sites of definitive hematopoiesis, including the aorta-gonad-mesonephros (AGM) mesenchyme, the hemogenic embryonic arterial endothelium, and hematopoietic clusters within the aorta, vitelline, and umbilical arteries. We inactivated the Meis1 gene in mice and found that Meis1 mutant mice die between embryonic days 11.5 and 14.5, showing internal hemorrhage, liver hypoplasia, and anemia. In Meis1 mutant mouse fetal liver and AGM, HSC compartments are severely underdeveloped and colony-forming potential is profoundly impaired. AGM mesenchymal cells expressing Runx1, an essential factor for definitive HSC specification, are almost absent in mutant mice. In addition, hematopoietic clusters in the dorsal aorta, vitelline, and umbilical arteries are reduced in size and number. These results show a requirement for Meis1 in the establishment of definitive hematopoiesis in the mouse embryo. Meis1 mutant mice also displayed complete agenesis of the megakaryocyte lineage and localized defects in vascular patterning, which may cause the hemorrhagic phenotype.