A brain-specific pgc1α fusion transcript affects gene expression and behavioural outcomes in mice

PGC1α is a transcriptional coactivator in peripheral tissues, but its function in the brain remains poorly understood. Various brain-specific Pgc1α isoforms have been reported in mice and humans, including two fusion transcripts (FTs) with non-coding repetitive sequences, but their function is unknown. The FTs initiate at a simple sequence repeat locus ∼570 Kb upstream from the reference promoter; one also includes a portion of a short interspersed nuclear element (SINE). Using publicly available genomics data, here we show that the SINE FT is the predominant form of Pgc1α in neurons. Furthermore, mutation of the SINE in mice leads to altered behavioural phenotypes and significant up-regulation of genes in the female, but not male, cerebellum. Surprisingly, these genes are largely involved in neurotransmission, having poor association with the classical mitochondrial or antioxidant programs. These data expand our knowledge on the role of Pgc1α in neuronal physiology and suggest that different isoforms may have distinct functions. They also highlight the need for further studies before modulating levels of Pgc1α in the brain for therapeutic purposes.

Heteroplasmy and paternally oriented shift of the organellar DNA composition in barley–wheat hybrids during backcrosses with wheat parents

Mitochondrial (mt) and chloroplast (ct) genome inheritance was studied in barley–wheat hybrids, as were their progenies obtained from backcrosses with different common wheat cultivars, by monitoring the composition of 4 mtDNA (coxI, a 5′-flanking region of cob, nad3-orf156, and 5′-upstream region of 18S/5S) and 2 ctDNA (simple-sequence repeat locus downstream of trnS and a 3′-flanking region of rbcL) loci. In male sterile F1 and BC1 plants, maternal barley mtDNA fragments were mainly detected and very low levels of paternal wheat fragments were occasionally detected by PCR in coxI, a 5′-flanking region of cob and nad3-orf156, whereas a 5′-upstream region of 18S/5S showed clear heteroplasmy, containing both maternal and paternal copies, with maternal copies prevailing. Plants showing such heteroplasmic mtDNA composition remained either semisterile or became completely sterile in the later backcross generations. Only maternal ctDNA copies were detected in these plants. In 3 stable, self-fertile, and vigourous lines obtained in the advanced backcross generations and possessing recombinant wheat nuclear genome, however, only mt- and ctDNA copies of wheat parents were detected; thus, the original alloplasmic condition appeared to be lost. Our results suggest that transmission followed by selective replication of the paternal wheat organellar DNA leads to a paternally oriented shift of the organellar DNA composition in barley–wheat hybrids, which correlates with the restoration of fertility and plant vigour. These 2 processes seem to be related to nucleocytoplasmic compatibility and to be under the control of the nuclear genome composition.Key words: barley–wheat hybrids, ctDNA, mtDNA, nucleoytoplasmic compatibility, organelle DNA inheritance.

A Detailed Linkage Map of Rainbow Trout Produced Using Doubled Haploids

We report the first detailed genetic linkage map of rainbow trout (Oncorhynchus mykiss). The segregation analysis was performed using 76 doubled haploid rainbow trout produced by androgenesis from a hybrid between the “OSU” and “Arlee” androgenetically derived homozygous lines. Four hundred and seventy-six markers segregated into 31 major linkage groups and 11 small groups (<5 markers/group). The minimum genome size is estimated to be 2627.5 cM in length. The sex-determining locus segregated to a distal position on one of the linkage groups. We analyzed the chromosomal distribution of three classes of markers: (1) amplified fragment length polymorphisms, (2) variable number of tandem repeats, and (3) markers obtained using probes homologous to the 5′ or 3′ end of salmonid-specific small interspersed nuclear elements. Many of the first class of markers were clustered in regions that appear to correspond to centromeres. The second class of markers were more telomeric in distribution, and the third class were intermediate. Tetrasomic inheritance, apparently related to the tetraploid ancestry of salmonid fishes, was detected at one simple sequence repeat locus and suggested by the presence of one extremely large linkage group that appeared to consist of two smaller groups linked at their tips. The double haploid rainbow trout lines and linkage map present a foundation for further genomic studies.