Recent Assembly of an Imprinted Domain from Non-Imprinted Components

Genomic imprinting, representing parent-specific expression of alleles at a locus, raises many questions about how—and especially why—epigenetic silencing of mammalian genes evolved. We present the first in-depth study of how a human imprinted domain evolved, analyzing a domain containing several imprinted genes that are involved in human disease. Using comparisons of orthologous genes in humans, marsupials, and the platypus, we discovered that the Prader-Willi/Angelman syndrome region on human Chromosome 15q was assembled only recently (105–180 million years ago). This imprinted domain arose after a region bearing UBE3A (Angelman syndrome) fused with an unlinked region bearing SNRPN (Prader-Willi syndrome), which had duplicated from the non-imprinted SNRPB/B′. This region independently acquired several retroposed gene copies and arrays of small nucleolar RNAs from different parts of the genome. In their original configurations, SNRPN and UBE3A are expressed from both alleles, implying that acquisition of imprinting occurred after their rearrangement and required the evolution of a control locus. Thus, the evolution of imprinting in viviparous mammals is ongoing

Senior Recital: Christian Fabrizio Artieda, jazz guitar

This recital is presented in partial fulfillment of requirements for the degree Bachelor of Music in Music Education. Mr. Artieda studies jazz guitar with Trey Wright.https://digitalcommons.kennesaw.edu/musicprograms/1137/thumbnail.jp

Assembly of the PWS-AS Imprinted Region in Placental Mammals during Vertebrate Evolution

<p>Relationships between fish, birds/reptiles, and the three mammal groups are presented as a phylogeny (top). In the ancestral arrangement, shared by marsupials, monotremes, birds, and fish, the block of imprinted human 15q genes (pink) is flanked by human X (green) and human 2 (purple) blocks. These three blocks were separated by at least two fissions and were rearranged next to an unlinked block of genes (on chick Chromosome 10, pale blue) to make up the present regions of human Chromosome 15q (and with two more inversions, of mouse Chromosome 7). <i>SNRPB′</i> (brown) is present on a different chromosome in fish, birds, and marsupials, but its duplicate <i>SNRPN</i> (orange) is transposed next to <i>UBE3A</i> in placentals. Other human 15q genes absent from non-placental vertebrates (orange) were independently added to the imprinted region in the placental lineage.</p

Biallelic Expression Demonstrated by Sequencing Brain cDNA from Heterozygous Animals for Alleles of <i>SNRPN</i> and <i>UBE3A</i> in Tammar Wallaby and <i>UBE3A</i> in Platypus

<p>Alleles differ at an A/T polymorphism at base pair 67 of the 3′ UTR of tammar <i>SNRPN,</i> a C/T polymorphism at base pair 247 of exon 5 in tammar <i>UBE3A,</i> and an insertion polymorphism of a C at base pair 179 of the 3′ UTR in platypus <i>UBE3A</i> (marked by boxes).</p

FISH Localization of BACs Containing Tammar Homologs of PWS-AS Genes

<p><i>UBE3A</i>/<i>CNGA3, GABRB3,</i> and <i>HERC2</i> localize to tammar wallaby Chromosome 5p and <i>SNRPN</i>/<i>SNRPB</i> to Chromosome 1q.</p