This chapter focuses on the cellular underpinnings of rapid adaptive color change in crustaceans.... more This chapter focuses on the cellular underpinnings of rapid adaptive color change in crustaceans. From the standpoint of molecular endocrinology, chromatic adaptation is pertinent to the physiological, cellular, and molecular biological mechanisms that regulate intracellular pigment granule movements. The chapter examines the distribution, organization, and ultrastructure of pigmentary effectors—the epidermal and internal chromatophores and retinal cells—and discusses the original characterization of pigment-aggregating and -dispersing chromatophorotropins that regulate pigment translocation and the sensory mechanisms that lead to their differential release from neurosecretory nuclei. Genes present in various arthropod groups code these peptide neurohormones, and their homology and conservation is discussed in light of evolutionary relationships with the Crustacea. An analysis of putative mechanisms of chromatophorotropin signal transduction is presented, focusing on membrane recept...
Crustacean color change results partly from granule aggregation induced by red pigment concentrat... more Crustacean color change results partly from granule aggregation induced by red pigment concentrating hormone (RPCH). In shrimp chromatophores, both the cyclic GMP (3', 5'-guanosine monophosphate) and Ca(2+) cascades mediate pigment aggregation. However, the signaling elements upstream and downstream from cGMP synthesis by GC-S (cytosolic guanylyl cyclase) remain obscure. We investigate post-RPCH binding events in perfused red ovarian chromatophores to disclose the steps modulating cGMP concentration, which regulates granule translocation. The inhibition of calcium/calmodulin complex (Ca(2+)/CaM) by N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) induces spontaneous aggregation but inhibits RPCH-triggered aggregation, suggesting a role in pigment aggregation and dispersion. Nitric oxide synthase inhibition by Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) strongly diminishes RPCH-induced aggregation; protein kinase G inhibition (by rp-cGMPs-triethylamine) re...
Developmental processes and their results, morphological characters, are inherited through transm... more Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes.
This chapter focuses on the cellular underpinnings of rapid adaptive color change in crustaceans.... more This chapter focuses on the cellular underpinnings of rapid adaptive color change in crustaceans. From the standpoint of molecular endocrinology, chromatic adaptation is pertinent to the physiological, cellular, and molecular biological mechanisms that regulate intracellular pigment granule movements. The chapter examines the distribution, organization, and ultrastructure of pigmentary effectors—the epidermal and internal chromatophores and retinal cells—and discusses the original characterization of pigment-aggregating and -dispersing chromatophorotropins that regulate pigment translocation and the sensory mechanisms that lead to their differential release from neurosecretory nuclei. Genes present in various arthropod groups code these peptide neurohormones, and their homology and conservation is discussed in light of evolutionary relationships with the Crustacea. An analysis of putative mechanisms of chromatophorotropin signal transduction is presented, focusing on membrane recept...
Crustacean color change results partly from granule aggregation induced by red pigment concentrat... more Crustacean color change results partly from granule aggregation induced by red pigment concentrating hormone (RPCH). In shrimp chromatophores, both the cyclic GMP (3', 5'-guanosine monophosphate) and Ca(2+) cascades mediate pigment aggregation. However, the signaling elements upstream and downstream from cGMP synthesis by GC-S (cytosolic guanylyl cyclase) remain obscure. We investigate post-RPCH binding events in perfused red ovarian chromatophores to disclose the steps modulating cGMP concentration, which regulates granule translocation. The inhibition of calcium/calmodulin complex (Ca(2+)/CaM) by N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W7) induces spontaneous aggregation but inhibits RPCH-triggered aggregation, suggesting a role in pigment aggregation and dispersion. Nitric oxide synthase inhibition by Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) strongly diminishes RPCH-induced aggregation; protein kinase G inhibition (by rp-cGMPs-triethylamine) re...
Developmental processes and their results, morphological characters, are inherited through transm... more Developmental processes and their results, morphological characters, are inherited through transmission of genes regulating development. While there is ample evidence that cis-regulatory elements tend to be modular, with sequence segments dedicated to different roles, the situation for proteins is less clear, being particularly complex for transcription factors with multiple functions. Some motifs mediating protein-protein interactions may be exclusive to particular developmental roles, but it is also possible that motifs are mostly shared among different processes. Here we focus on HoxA13, a protein essential for limb development. We asked whether the HoxA13 amino acid sequence evolved similarly in three limbless clades: Gymnophiona, Amphisbaenia and Serpentes. We explored variation in ω (dN/dS) using a maximum-likelihood framework and HoxA13sequences from 47 species. Comparisons of evolutionary models provided low ω global values and no evidence that HoxA13 experienced relaxed selection in limbless clades. Branch-site models failed to detect evidence for positive selection acting on any site along branches of Amphisbaena and Gymnophiona, while three sites were identified in Serpentes. Examination of alignments did not reveal consistent sequence differences between limbed and limbless species. We conclude that HoxA13 has no modules exclusive to limb development, which may be explained by its involvement in multiple developmental processes.
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Papers by Sarah Milograna