Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Increased interleukin-1alpha and interleukin-1beta production by macrophages of low-density lipoprotein receptor knock-out mice stimulated with lipopolysaccharide is CD11c/CD18-receptor mediated.

Immune mechanisms, including production of pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF), play an important role in early atherogenesis. The study of the mechanisms responsible for the increased cytokine production capacity of hypercholesterolemic hosts is therefore crucial for finding new strategies aimed to stop the development of atherosclerosis. We assessed the lipopolysaccharide (LPS)-induced cytokine production of macrophages from low-density lipoproteins (LDL)-receptor knock-out (LDLR-/-) mice, which have a seven- to ninefold higher plasma LDL concentration. Macrophages of LDLR-/- mice produced approximately twofold more IL-1alpha and IL-1beta in response to LPS when compared with macrophages of control mice (LDLR+/+). TNF-alpha synthesis was only slightly increased. Removal of CD14 by phospholipase C treatment of cells decreased cytokine production by 50% (IL-1) to 80% (TNF), but the differences between LDLR-/- and LDLR+/+ remained the same. In contrast, treatment of cells with anti-CD11c monoclonal antibody inhibited the IL-1alpha and IL-1beta production in LDLR-/- mice towards normal values, while no effect could be seen on TNF. In conclusion, LDLR-/- macrophages stimulated with LPS synthesize more IL-1alpha and IL-1beta than controls and this phenomenon is mediated by the CD11c/CD18 receptor.     

Cryopreservation of human oocytes: a review of current problems and perspectives

It is well recognized that the ability to cryopreserve unfertilizedhuman oocytes would make a significant contribution to infertilitytreatment. However, despite considerable interest, very fewsuccessful pregnancies have arisen from cryopreserved oocytesafter thawing, insemination and transfer of the subsequent embryo.The reasons for this lack of progress may well result from adearth of information on how the various biophysical changesduring a cryopreservation regimen affect human oocyte function.Recently, fundamental studies on the effects of cooling, membranepermeability, cryoprotectant addition and ice formation havebeen performed on human oocytes by a number of groups, and theseform the basis of the current review. It is likely that successfulhuman oocyte cryopreservation will only follow once these factorsare fully understood, but the existing base of knowledge shouldprovide a platform for further improvements in the techniquescurrently employed.