MicroRNAs are ∼22 nucleotide endogenous noncoding RNAs that post-transcriptionally repress expression of protein-coding genes by base-pairing with the 3′-untranslated regions of the target mRNAs. We present here an inventory of miRNA expression profiles from 13 neuroanatomically distinct areas of the adult mouse central nervous system (CNS). Microarray profiling in combination with real-time RT-PCR and LNA (locked nucleic acid)-based in situ hybridization uncovered 44 miRNAs displaying more than threefold enrichment in the spinal cord, cerebellum, medulla oblongata, pons, hypothalamus, hippocampus, neocortex, olfactory bulb, eye, and pituitary gland. These findings suggest that a large number of mouse CNS-expressed miRNAs may be associated with specific functions within these regions. Notably, more than 50% of the identified mouse CNS-enriched miRNAs showed different expression patterns compared to those reported in zebrafish, although the mature miRNA sequences are nearly 100% conserved between the two vertebrate species. The inventory of miRNA profiles in the adult mouse CNS presented here provides an important step toward further elucidation of miRNA function and miRNA-related gene regulatory networks in the mammalian central nervous system.

Atrial natriuretic peptide (ANP) is an important regulator of arterial blood pressure. The mechanisms mediating its hypotensive effects are complex and involve the inhibition of the sympathetic and renin-angiotensin-aldosterone (RAA) systems, increased diuresis/natriuresis, vasodilation, and enhanced vascular permeability. In particular, the contribution of the direct vasodilating effect of ANP to the hypotensive actions remains controversial, because variable levels of the ANP receptor, guanylyl cyclase A (GC-A), are expressed in different vascular beds. The objective of our study was to determine whether a selective deletion of GC-A in vascular smooth muscle would affect the hypotensive actions of ANP. We first created a mutant allele of mouse GC-A by flanking a required exon with loxP sequences. Crossing floxed GC-A with SM22-Cre transgene mice expressing Cre recombinase in smooth muscle cells (SMC) resulted in mice in which vascular GC-A mRNA expression was reduced by ≈80%. Accordingly, the relaxing effects of ANP on isolated vessels from these mice were abolished; despite this fact, chronic arterial blood pressure of awake SMC GC-A KO mice was normal. Infusion of ANP caused immediate decreases in blood pressure in floxed GC-A but not in SMC GC-A knockout mice. Furthermore, acute vascular volume expansion, which causes release of cardiac ANP, did not affect resting blood pressure of floxed GC-A mice, but rapidly and significantly increased blood pressure of SMC GC-A knockout mice. We conclude that vascular GC-A is dispensable in the chronic and critical in the acute moderation of arterial blood pressure by ANP.

The S100A9 (MRP14) protein is abundantly expressed in myeloid cells and has been associated with various inflammatory diseases. The S100A9-deficient mice described here were viable, fertile, and generally of healthy appearance. The myelopoietic potential of the S100A9-null bone marrow was normal. S100A8, the heterodimerization partner of S100A9 was not detectable in peripheral blood cells, suggesting that even a deficiency in both S100A8 and S100A9 proteins was compatible with viable and mature neutrophils. Surprisingly, the invasion of S100A9-deficient leukocytes into the peritoneum and into the skin in vivo was indistinguishable from that in wild-type mice. However, stimulation of S100A9-deficient neutrophils with interleukin-8 in vitro failed to provoke an up-regulation of CD11b. Migration upon a chemotactic stimulus through an endothelial monolayer was markedly diminished in S100A9-deficient neutrophils. Attenuated chemokinesis of the S100A9-deficient neutrophils was observed by using a three-dimensional collagen matrix migration assay. The altered migratory behavior was associated with a microfilament system that was highly polarized in unstimulated S100A9-deficient neutrophils. Our data suggest that loss of the calcium-binding S100A9 protein reduces the responsiveness of the neutrophils upon chemoattractant stimuli at least in vitro. Alternative pathways for neutrophil emigration may be responsible for the lack of any effect in the two in vivo models we have investigated so far.

Prader-Willi syndrome (PWS [MIM 176270]) is a neurogenetic disorder characterized by decreased fetal activity, muscular hypotonia, failure to thrive, short stature, obesity, mental retardation, and hypogonadotropic hypogonadism. It is caused by the loss of function of one or more imprinted, paternally expressed genes on the proximal long arm of chromosome 15. Several potential PWS mouse models involving the orthologous region on chromosome 7C exist. Based on the analysis of deletions in the mouse and gene expression in PWS patients with chromosomal translocations, a critical region (PWScr) for neonatal lethality, failure to thrive, and growth retardation was narrowed to the locus containing a cluster of neuronally expressed MBII-85 small nucleolar RNA (snoRNA) genes. Here, we report the deletion of PWScr. Mice carrying the maternally inherited allele (PWScr^m−/p+) are indistinguishable from wild-type littermates. All those with the paternally inherited allele (PWScr^m+/p−) consistently display postnatal growth retardation, with about 15% postnatal lethality in C57BL/6, but not FVB/N crosses. This is the first example in a multicellular organism of genetic deletion of a C/D box snoRNA gene resulting in a pronounced phenotype. Prader-Willi syndrome, or PWS, is a complex neurogenetic disorder and the most common genetic cause of life-threatening childhood obesity. Newborns have poor muscle tone, making suckling difficult, which leads to poor weight gain. After infancy, they experience extreme hunger, leading to obesity. Other symptoms include short stature, mental retardation, and often infertility. In PWS patients, a complex set of genes on the paternal chromosome 15 (in the PWS region) is missing or unexpressed. In an attempt to understand this disorder, various protein-coding genes in this region have been deleted in mice, but none of the resulting phenotypes consistently correlated with the human disease. This region also contains a cluster of genes that encode functional non-protein-coding RNAs. We deleted specifically the MBII-85 small nucleolar RNA (snoRNA) gene cluster on the parental mouse chromosome, which did not affect expression of any of the other snoRNA or protein-coding genes in the PWS region. These mice consistently displayed postnatal growth retardation starting from day 5 to 6, low postnatal lethality only in certain genetic backgrounds (<15%), and no adolescent obesity. Thus, this mouse model, with the deletion of a small, brain-specific non-protein-coding RNA, should prove useful for teasing out the various molecular pathologies of PWS.