A single copy of carbonic anhydrase 2 restores wild-type circadian period to carbonic anhydrase II-deficient mice

Carbonic anhydrase II deficiency

Carbonic anhydrase II deficiency (OMIM # 259730), initially called "osteopetrosis with renal tubular acidosis and cerebral calcification syndrome", reveals an important role for the enzyme carbonic anhydrase II (CA II) in osteoclast and renal tubule function. Discovered in 1972 and subsequently given various names, CA II deficiency now describes >100 affected individuals encountered predominantly from the Middle East and Mediterranean region. In 1983, CA II deficiency emerged as the first osteopetrosis (OPT) understood metabolically, and in 1991 the first understood molecularly. CA II deficiency is the paradigm OPT featuring failure of osteoclasts to resorb bone due to inability to acidify their pericellular milieu. The disorder presents late in infancy or early in childhood with fracturing, developmental delay, weakness, short stature, and/or cranial nerve compression and palsy. Mental retardation is common. The skeletal findings may improve by adult life, and CA II deficiency can be associated with a normal life-span. Therefore, it has been considered an "intermediate" type of OPT. In CA II deficiency, OPT is uniquely accompanied by renal tubular acidosis (RTA) of proximal, distal, or combined type featuring hyperchloremic metabolic acidosis, rarely with hypokalemia and paralysis. Cerebral calcification uniquely appears in early childhood. The etiology is bi-allelic loss-of-function mutations of CA2 that encodes CA II. Prenatal diagnosis requires mutational analysis of CA2. Although this enzymopathy reveals how CA II is important for the skeleton and kidney tubule, the pathogenesis of the mental subnormality and cerebral calcification is less well understood. Several mouse models of CA II deficiency have shown growth hormone deficiency, yet currently there is no standard pharmacologic therapy for patients. Treatment of the systemic acidosis is often begun when growth is complete. Although CA II deficiency is an "osteoclast-rich" OPT, and therefore transplantation of healthy osteoclasts can improve the skeletal disease, the RTA and central nervous system difficulties persist.

Circadian Analysis of the Mouse Cerebellum Proteome

The cerebellum contains a circadian clock, generating internal temporal signals. The daily oscillations of cerebellar proteins were investigated in mice using a large-scale two-dimensional difference in gel electrophoresis (2D-DIGE). Analysis of 2D-DIGE gels highlighted the rhythmic variation in the intensity of 27/588 protein spots (5%) over 24 h based on cosinor regression. Notably, the rhythmic expression of most abundant cerebellar proteins was clustered in two main phases (i.e., midday and midnight), leading to bimodal distribution. Only six proteins identified here to be rhythmic in the cerebellum are also known to oscillate in the suprachiasmatic nuclei, including two proteins involved in the synapse activity (Synapsin 2 [SYN2] and vesicle-fusing ATPase [NSF]), two others participating in carbohydrate metabolism (triosephosphate isomerase (TPI1] and alpha-enolase [ENO1]), Glutamine synthetase (GLUL), as well as Tubulin alpha (TUBA4A). Most oscillating cerebellar proteins were not previously identified in circadian proteomic analyses of any tissue. Strikingly, the daily accumulation of mitochondrial proteins was clustered to the mid-resting phase, as previously observed for distinct mitochondrial proteins in the liver. Moreover, a number of rhythmic proteins, such as SYN2, NSF and TPI1, were associated with non-rhythmic mRNAs, indicating widespread post-transcriptional control in cerebellar oscillations. Thus, this study highlights extensive rhythmic aspects of the cerebellar proteome.

Brain region-specific gene expression changes after chronic intermittent ethanol exposure and early withdrawal in C57BL/6J mice

Neuroadaptations that participate in the ontogeny of alcohol dependence are likely a result of altered gene expression in various brain regions. The present study investigated brain region-specific changes in the pattern and magnitude of gene expression immediately following chronic intermittent ethanol (CIE) exposure and 8 hours following final ethanol exposure [i.e. early withdrawal (EWD)]. High-density oligonucleotide microarrays (Affymetrix 430A 2.0, Affymetrix, Santa Clara, CA, USA) and bioinformatics analysis were used to characterize gene expression and function in the prefrontal cortex (PFC), hippocampus (HPC) and nucleus accumbens (NAc) of C57BL/6J mice (Jackson Laboratories, Bar Harbor, ME, USA). Gene expression levels were determined using gene chip robust multi-array average followed by statistical analysis of microarrays and validated by quantitative real-time reverse transcription polymerase chain reaction and Western blot analysis. Results indicated that immediately following CIE exposure, changes in gene expression were strikingly greater in the PFC (284 genes) compared with the HPC (16 genes) and NAc (32 genes). Bioinformatics analysis revealed that most of the transcriptionally responsive genes in the PFC were involved in Ras/MAPK signaling, notch signaling or ubiquitination. In contrast, during EWD, changes in gene expression were greatest in the HPC (139 genes) compared with the PFC (four genes) and NAc (eight genes). The most transcriptionally responsive genes in the HPC were involved in mRNA processing or actin dynamics. Of the few genes detected in the NAc, the most representatives were involved in circadian rhythms. Overall, these findings indicate that brain region-specific and time-dependent neuroadaptive alterations in gene expression play an integral role in the development of alcohol dependence and withdrawal.

Pressed for time: the circadian clock and hypertension

Hypertension is a major risk factor for cardiovascular disease and death. The "silent" rise of blood pressure that occurs over time is largely asymptomatic. However, its impact is deafening-causing and exacerbating cardiovascular disease, end-organ damage, and death. The present article addresses recent observations from human and animal studies that provide new insights into how the circadian clock regulates blood pressure, contributes to hypertension, and ultimately evolves vascular disease. Further, the molecular components of the circadian clock and their relationship with locomotor activity, metabolic control, fluid balance, and vascular resistance are discussed with an emphasis on how these novel, circadian clock-controlled mechanisms contribute to hypertension.

A QTL on mouse chromosome 12 for the genetic variance in free-running circadian period between inbred strains of mice

Background

Many genes control circadian period in mice. Prior studies suggested a quantitative trait locus (QTL) on proximal mouse chromosome 12 for interstrain differences in circadian period. Since the B6.D2NAhr^d/J strain has DBA/2 alleles for a portion of proximal chromosome 12 introgressed onto its C57BL/6J background, we hypothesized that these mice would have a shorter circadian period than C57BL/6J mice.

Methods

We compared circadian phenotypes of B6.D2NAhr^d/J and C57BL/6 mice: period of general locomotor activity in constant dark and rest/activity pattern in alternating light and dark. We genotyped the B6.D2NAhr^d/J mice to characterize the size of the genomic insert. To aid in identifying candidate quantitative trait genes we queried databases about the resident SNPs, whole brain gene expression in C57BL/6J versus DBA/2J mice, and circadian patterns of gene expression.

Results

The B6.D2NAhr^d/J inbred mice have a shorter circadian period of locomotor activity than the C57BL/6J strain. Furthermore, the genomic insert is associated with another phenotype: the mean phase of activity minimum in the dark part of a light-dark lighting cycle. It was one hour later than in the background strain. The B6.D2NAhr^d/J mice have a DBA/2J genomic insert spanning 35.4 to 41.0 megabase pairs on Chromosome 12. The insert contains 15 genes and 12 predicted genes. In this region Ahr (arylhydrocarbon receptor) and Zfp277 (zinc finger protein 277) both contain non-synonymous SNPs. Zfp277 also showed differential expression in whole brain and was cis-regulated. Three genes and one predicted gene showed a circadian pattern of expression in liver, including Zfp277.

Conclusion

We not only fine-mapped the QTL for circadian period on chromosome 12 but found a new QTL there as well: an association with the timing of the nocturnal activity-minimum. Candidate quantitative trait genes in this QTL are zinc finger protein 277 and arylhydrocarbon receptor. Arylhydrocarbon receptor is structurally related to Bmal1, a canonical clock gene.