Abstracts - Society for Developmental Biology

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into the role snx5 playsin the Notch pathway, represent intriguing ideas about the precise control of developmental
signaling by miRNAs.
Program/Abstract # 239
Identification and characterization of a long-range enhancer element in the dPax2 cone cell specific enhancer
sparkling
Evans, Nicole C.; Strom, Amy; Barolo, Scott, University of Michigan, Ann Arbor, United States
Enhancers are cis-regulatory elements that control gene expression and patterning during development. As enhancers are
often located at considerable genomic distances from their target genes, distal enhancer promoter interactions are a crucial
part of transcriptional regulation, yet surprisingly little is known about how these interactions are facilitated in vivo. To
better understand this essential enhancer function we have undertaken a novel in vivo analysis of the EGFR/MAPK- and
Notch- regulated dPax2 cone cell-specific sparkling enhancer (spa) and its ability to activate gene expression from both a
promoter proximal, and distal position. In this study reporter gene expression is driven by the spa enhancer placed either
adjacent to, or at a distance from, a heterologous promoter. Using this approach, we have identified a sequence within spa
that is required when the enhancer is placed at a distance from the promoter, but is dispensable when the enhancer is
proximal to the promoter. As this DNA sequence appears to convey long-range enhancer activity to the sparkling enhancer
we refer to it as the “remote control” element or RCE. Our current work focuses on determining the functional properties
and capabilities of the RCE, as well as the identification and characterization of proteins that interact with the RCE and
allow it to perform its essential activities. This study will allow us to better understand the mechanisms by which enhancers
engage in long-range transcriptional regulation.
Program/Abstract # 240
Multiple enhancers integrate patterning signals to drive rhombomere-specific gene expression in the hindbrain
Gongal, Patricia, Ecole Normale Superieure Insitut de Biologie, Paris, France; Labalette, Charlotte; Le Men, Johan;
Bouchoucha, Yassine; Gilardi-Hebenstreit, Pascale; Charnay, Patrick (Paris, France)
Proper patterning of the neural tube along the anterior-posterior (A-P) axis is essential for the correct specification of
neuronal fate during development. A complex network of signaling molecules and transcription factors regulating this
process has been identified. However, the interactions between diverse signaling networks and the cis-regulatory elements
that drive cell type-specific transcription remain poorly understood. Among the key regulators of vertebrate A-P patterning
is the transcription factor Krox20, whose activity is required for hindbrain segmentation and the specification of
rhombomeres 3 (r3) and 5 (r5). We have identified two enhancers that drive krox20 expression in r5, termed Elements B
and C. Using transgenic reporter lines in zebrafish, we have found that the two enhancers drive transcriptional activity in
rhombomere 5 with unique temporal and spatial profiles. While Element B initiates expression at the end of gastrulation, it
is mainly active at later stages in the ventral part of ther hombomere. In contrast, Element C is active in only a small subset
of r5 cells until mid-somitogenesis, when it increasingly drives transcription in the dorsal part of the rhombomere.
Although activated in fewer cells within r5, mouse knockout experiments indicate Element C is essential for this
rhombomere’s development. We also demonstrate that the two regulatory elements differ in their response to and their
requirement for signals known to regulate krox20 expression in r5, including Hox proteins, FGF, Mafb, and vHNF1.
Together, our work suggests that multiple enhancers, possibly acting via unique mechanisms in different rhombomere subterritories,
are required to establish segmental gene expression.
Program/Abstract # 241
Identification of a 2.1 Mb region associated with the rumpless phenotype in the Araucana chicken breed
Freese, Nowlan H., Clemson University Biological SciencesClemson, United States; Noorai, Rooksana; Clark, Leigh Ann;
Chapman, Susan (Clemson University, Clemson, SC, United States)
The Araucana chicken breed is characterized by a rumpless phenotype, caused by the caudal-most vertebrae not forming.
This trait is inherited in an autosomal dominant fashion. We isolated genomic DNA from 60 Araucana from 6 separate
flocks with rumpless, tailed, or partially tailed phenotypes. To identify genomic regions associated with the rumpless
phenotype, we conducted a genome wide association study (GWAS) using Illumina 60k SNP (single nucleotide
polymorphism) BeadChips. Case/control analysis with 41 rumpless and 14 tailed Araucana was carried out for 56,685
SNPs. Correction for false positive results was accomplished using 100,000 per mutations of the association analysis. The
10 most significant p genome values were obtained for SNPs on chromosome 2. A haplotype block of 2.1 Mb surrounding
these and other supporting SNPs was identified in the rumpless Araucana population. We hypothesize that the causative
mutation for the rumpless phenotype lies within this haplotype block. Evaluation of candidate genes and validation of the
mutation responsible for the rumpless Araucana phenotype is underway.