RESUMO
The zebrafish adult pigment pattern has emerged as a useful model for understanding the development and evolution of adult form as well as pattern-forming mechanisms more generally. In this species, a series of horizontal melanophore stripes arises during the larval-to-adult transformation, but the genetic and cellular bases for stripe formation remain largely unknown. Here, we show that the seurat mutant phenotype, consisting of an irregular spotted pattern, arises from lesions in the gene encoding Immunoglobulin superfamily member 11 (Igsf11). We find that Igsf11 is expressed by melanophores and their precursors, and we demonstrate by cell transplantation and genetic rescue that igsf11 functions autonomously to this lineage in promoting adult stripe development. Further analyses of cell behaviors in vitro, in vivo, and in explant cultures ex vivo demonstrate that Igsf11 mediates adhesive interactions and that mutants for igsf11 exhibit defects in both the migration and survival of melanophores and their precursors. These findings identify the first in vivo requirements for igsf11 as well as the first instance of an immunoglobulin superfamily member functioning in pigment cell development and patterning. Our results provide new insights into adult pigment pattern morphogenesis and how cellular interactions mediate pattern formation.
Assuntos
Padronização Corporal/genética , Moléculas de Adesão Celular/genética , Proteínas de Peixes/genética , Imunoglobulinas/genética , Melanóforos/metabolismo , Pigmentação/genética , Proteínas de Peixe-Zebra/genética , Peixe-Zebra/genética , Animais , Evolução Biológica , Diferenciação Celular , Movimento Celular , Sobrevivência Celular , Embrião não Mamífero , Regulação da Expressão Gênica no Desenvolvimento , Larva/genética , Melanóforos/citologia , Melanóforos/transplante , Mutação , FenótipoRESUMO
Frog melanophores rapidly change colour by dispersion or aggregation of melanosomes. A long-term colour change exists where melanosomes are released from melanophores and transferred to surrounding skin cells. No in vitro model for pigment transfer exists for lower vertebrates. Frog melanophores of different morphology exist both in epidermis where keratinocytes are present and in dermis where fibroblasts dominate. We have examined whether release and transfer of melanosomes can be studied in a melanophore-fibroblast co-culture, as no frog keratinocyte cell line exists. Xenopus laevis melanophores are normally cultured in conditioned medium from fibroblasts and fibroblast-derived factors may be important for melanophore morphology. Melanin was exocytosed as membrane-enclosed melanosomes in a process that was upregulated by alpha-melanocyte-stimulating hormone (alpha-MSH), and melanosomes where taken up by fibroblasts. Melanosome membrane-proteins seemed to be of importance, as the cluster-like uptake pattern of pigment granules was distinct from that of latex beads. In vivo results confirmed the ability of dermal fibroblasts to engulf melanosomes. Our results show that cultured frog melanophores can not only be used for studies of rapid colour change, but also as a model system for long-term colour changes and for studies of factors that affect pigmentation.
Assuntos
Derme/fisiologia , Epiderme/fisiologia , Fibroblastos/fisiologia , Queratinócitos/fisiologia , Melanóforos/transplante , Pigmentação/fisiologia , Animais , Linhagem Celular Transformada , Técnicas de Cocultura , Derme/citologia , Endocitose/efeitos dos fármacos , Endocitose/fisiologia , Epiderme/ultraestrutura , Fibroblastos/ultraestrutura , Queratinócitos/ultraestrutura , Melaninas/metabolismo , Melanóforos/fisiologia , Melanóforos/ultraestrutura , Modelos Biológicos , Pigmentação/efeitos dos fármacos , Xenopus laevis , alfa-MSH/metabolismo , alfa-MSH/farmacologiaRESUMO
The influence of environmental stimuli on a daily rhythm of immune activity during scale allograft rejection was investigated in gulf killifish, Fundulus grandis. Although melanophore destruction in the grafts is largely restricted to the scotophases in killifish held on 12 h daily photoperiods (LD 12:12), timed daily netting (tank-transfer "stress"), thermoperiods (from 20 degrees to 30 degrees C for 4 or 12 h), and feeding altered the expression of this rhythm. Melanophore breakdown peaked 0-12 h after netting or thermoperiod onset and 12-24 h after feeding, whether the fish were exposed to these nonphotic daily stimuli at the onset or offset of 12-h photoperiods. In fish held under continuous light and pretreated with these daily stimuli, 24-h immune activity rhythms persisted in the altered phases for several days after the daily treatments were stopped. These findings suggest that a daily rhythm of immune activity may have adaptive significance in fish.
Assuntos
Ritmo Circadiano/imunologia , Rejeição de Enxerto/imunologia , Peixes Listrados/imunologia , Animais , Feminino , Luz , Melanóforos/transplante , Transplante Homólogo/imunologiaRESUMO
The effects of gamma-irradiation on allograft rejection in the teleost, Oryzias latipes, were examined at 25 degrees C. The survival of melanophores in the transplanted scale was observed as an index of rejection. Allografts were rejected in non-irradiated fish within 7 days. In the gamma-irradiated recipients (2kR), the grafts were rejected more slowly, but still within 20 days. The gamma-ray effects, however, disappeared almost completely within 25 days after the irradiation. If the same recipient again received transplants, the secondary response occurred clearly and the melanophores were rejected very rapidly. The secondary response was suppressed by gamma-rays if the fish was irradiated just before the second transplantation. Immunologic memory against the first transplants disappeared within 30 days, a period shorter than that of mammals.