Expression and regulation of groucho‐related genes in the embryonic chicken feather bud

Abstract

The groucho-related gene (Grg) products modulate the transcriptional response to several extracellular signals, including the Wnts. In an effort to define the roles of Grgs in the morphogenesis of the feather bud, cDNAs encoding members of the Grg family were cloned from embryonic chick skin. In situ hybridization was used to localize transcripts for cGrg2, Grg3, Grg4, and Grg5 in embryos from day 6 through day 9. Expression of cGrg2, 3, and 5 is detected throughout the initial epidermal placode. As the buds mature, expression becomes limited to the posterior halves and eventually to the distal tip of the outgrowing bud. This pattern and the effects of forced activation of the bone morphogenetic protein and ␤-catenin signal transduction pathways on Grg gene expression suggest that these genes act downstream of the early activation of the ␤-catenin pathway that initiates placode formation. Induction of Grg genes by ␤-catenin may serve as a negative feedback to modulate pathway activation while also altering the activity of other transduction pathways involved in bud patterning. Developmental Dynamics 226:587-595, 2003.

Extrinsic versus intrinsic cues in avian paraxial mesoderm patterning and differentiation

“…The myotome seems to have solved this problem by expressing the negative regulator of Shh signalling, Hip, in response to Shh signalling (Chuang and McMahon, 1999). Similarly, the Tcf/Lef corepressors of the Groucho family are expressed in the myotome (Daniels and Weis, 2005; Van Hateren et al, 2005), possibly upon Wnt signalling (Houghton et al, 2003). Thus, signalling molecules regulate the levels of signalling via negative feedback loops.…”

Differential regional expression of multiple ADAMs during feather bud formation

“…Avian feathers represent an integumental system that is adapted to a great variety of biological needs (Meyer and Baumgärtner, 1998). The formation of feather buds is the result of an exchange of signals between the dermis and epidermis; it represents an accessible model to investigate gene functional activity, signal transduction, and the molecular interaction of skin components (Houghton et al, 2003). Feather bud formation takes place in several developmental steps.…”

“…During feather bud formation, cell density in the dermis increases initially at fixed positions within the presumptive feather tract; this process then spreads through the entire feather tract (Houghton et al, 2003). Within the thickened epidermal placode, bud and interbud regions form in response to inductive signals from the dermis.…”

“…Interactions between the epidermis and the dermis regulate further bud development (Houghton et al, 2003, 2005). The molecules that are involved in feather bud formation, either through positive or a negative regulatory mechanisms, include growth factors, homeobox genes, cell adhesion molecules, extracellular matrix molecules like matrix metalloprotease, and transcription factors (Chuong, 1993; Widelitz et al, 1997; Dohrmann et al, 2002; Houghton et al, 2003, 2005; Rouzankina et al, 2004; Obinata and Akimoto, 2005; Drew et al, 2007; Michon et al, 2007, 2008; Jiang et al, 2011). To better understand the process of the bud formation, we studied members of the ADAM (a disintegrin and metalloprotease) family and identified them as additional molecular players in feather bud formation.…”

Wnt Signaling in Lymphopoiesis

“…Consistent with this possibility, the repression of the E-cadherin promoter by LEF1 and Groucho was found to occur in the presence of b-catenin (Jamora et al 2003). In addition, recent data indicate that the expression of Groucho is induced in cells of chick feather buds, in which active Wnt signaling occurs (Houghton et al 2003). This observation raises the possibility that Wnt signaling and b-catenin stabilization mediate LEF1/TCF-dependent repression indirectly via an induction of Groucho.…”