Developmental and daily expression of the Pax4 and Pax6 homeobox genes in the rat retina: localization of Pax4 in photoreceptor cells

Authors

  • Martin F. Rath,

    1. Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark
    2. Program in Developmental Endocrinology and Genetics, Section on Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
    Search for more papers by this author
  • Michael J. Bailey,

    1. Program in Developmental Endocrinology and Genetics, Section on Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
    Search for more papers by this author
    • 1

      The present address of Michael J. Bailey is the Department of Poultry Science, Texas A&M University, College Station, TX, USA.

  • Jong-So Kim,

    1. Program in Developmental Endocrinology and Genetics, Section on Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
    Search for more papers by this author
    • 2

      The present address of Jong-So Kim is the Department of Life Science, Pohang University of Science and Technology, Pohang, South Korea.

  • Steven L. Coon,

    1. Program in Developmental Endocrinology and Genetics, Section on Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
    Search for more papers by this author
  • David C. Klein,

    1. Program in Developmental Endocrinology and Genetics, Section on Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
    Search for more papers by this author
  • Morten Møller

    1. Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, Copenhagen, Denmark
    Search for more papers by this author

Address correspondence and reprint requests to Martin Fredensborg Rath, Department of Neuroscience and Pharmacology, Panum Institute, University of Copenhagen, 24.3.37, Blegdamsvej 3, Copenhagen DK-2200, Denmark. E-mail: mrath@sund.ku.dk

Abstract

Pax4 is a homeobox gene encoding Pax4, a transcription factor that is essential for embryonic development of the endocrine pancreas. In the pancreas, Pax4 counters the effects of the related transcription factor, Pax6, which is known to be essential for eye morphogenesis. In this study, we have discovered that Pax4 is strongly expressed in retinal photoreceptors of the rat. Pax4 expression is not detectable in the foetal eye; however, postnatal Pax4 transcript levels rapidly increase. In contrast, Pax6 exhibits an inverse developmental pattern of expression being more strongly expressed in the foetal eye. Histological analysis revealed that Pax4 mRNA is exclusively expressed in the retinal photoreceptors, whereas Pax6 mRNA and protein are present in the inner nuclear layer and in the ganglion cell layer of the mature retina. In the adult retina, Pax4 transcripts exhibit a diurnal rhythm with maximal levels occurring during the light period, whereas retinal Pax6 transcript levels do not change throughout the day. The daily changes in Pax4 expression may contribute to daily changes in function in the differentiated retinal photoreceptor.

Ancillary