Characterisation of the GH gene cluster in a new-world monkey, the marmoset (Callithrix jacchus)

In most mammals pituitary GH is encoded by a single gene with no close relatives. However, in man the GH gene has been shown to be one of a cluster of five closely related genes, four of which are expressed in the placenta. Rhesus monkey also expresses at least five closely related GH-like genes, although the genomic organisation of these has not been fully reported. Here we describe the cloning and characterisation of GH-like genes in a new-world monkey, the marmoset (Callithrix jacchus). This species possesses a cluster of eight GH-like 'genes'. The gene at the 5' end of this cluster encodes pituitary GH and is similar to that encoding human GH. Five of the eight marmoset 'genes' are probably pseudogenes, since they include mutations which would prevent normal expression, including stop codons and small insertions/deletions that would change the reading frame. In one case a large part of a gene is deleted, and in another a large insertion is introduced into an exon. The remaining two marmoset genes are potentially expressible, as proteins with sequences substantially different (at 25-30% of all residues) from that of marmoset GH itself; whether and in which tissue(s) such expression actually occurs is not yet known. None of the marmoset genes is clearly equivalent to any of the human GH-like genes expressed in the placenta, and this and phylogenetic analysis suggest that the duplications that gave rise to the marmoset GH gene cluster occurred independently of those that gave rise to the corresponding cluster in man. Although it includes more 'genes', the marmoset cluster extends over a shorter region of chromosomal DNA (about 35 kb) than does the human GH gene cluster (about 50 kb).

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Parcellation of the frontal cortex of the New World monkey Callithrix jacchus by eight neurotransmitter-binding sites

Anatomy and Embryology ◽

10.1007/bf00186741 ◽

1995 ◽

Vol 191 (6) ◽

Cited By ~ 14

Author(s):

R. Gebhard ◽

K. Zilles ◽

A. Schleicher ◽

B.J. Everitt ◽

T.W. Robbins ◽

...

Keyword(s):

Frontal Cortex ◽

Binding Sites ◽

New World ◽

World Monkey ◽

Callithrix Jacchus ◽

New World Monkey

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Topography of ganglion cells and photoreceptors in the retina of a New World monkey: The marmoset Callithrix jacchus

Visual Neuroscience ◽

10.1017/s0952523800007586 ◽

1996 ◽

Vol 13 (2) ◽

pp. 335-352 ◽

Cited By ~ 87

Author(s):

Heath D. Wilder ◽

Ulrike Grünert ◽

Barry B. Lee ◽

Paul R. Martin

Keyword(s):

New World ◽

Ganglion Cells ◽

World Monkey ◽

Pcr Amplification ◽

Spatial Vision ◽

Macaque Monkey ◽

Callithrix Jacchus ◽

Peripheral Retina ◽

Spatial Density ◽

New World Monkey

AbstractWe studied the anatomical substrates of spatial vision in a New World monkey, the marmoset Callithrix jacchus. This species has good visual acuity and a foveal specialization which is qualitatively similar to that of humans and other Old World primates.We measured the spatial density of retinal ganglion cells and photoreceptors, and calculated the relative numbers of these cell populations. We find that ganglion cells outnumber photoreceptors by between 2.4:1 and 4.2:1 in the fovea. The peak sampling density of ganglion cells is close to 550,000 cells/mm2. This value falls by almost 1000-fold between the fovea and peripheral retina; a value which approaches recent estimates of the centroperipheral ganglion cell gradient for human and macaque monkey retina and primary visual cortex. The marmoset shows a sex-linked polymorphism of color vision: all male and some female marmosets are dichromats. Six of the retinas used in the present study came from animals whose chromatic phenotype was identified in electrophysiological experiments and confirmed by polymerase chain reaction (PCR) amplification of cone opsin encoding genes. One animal was a trichromat and the others were dichromats. Antibodies against short wavelength-sensitive (SWS) cones labeled close to 8% of all cones near the fovea of onedichromat animal, consistent with electrophysiological evidence that the SWS system is present inall marmosets. The topography and spatial density of cone photoreceptors and ganglion cells was similar to that reported for macaque retina, and we found no obvious difference between dichromatic and trichromatic marmoset retinas. These results reinforce the view that the main determinate of primate foveal topography is the requirement for maximal spatial resolution.

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Segregation of Receptive Field Properties in the Lateral Geniculate Nucleus of a New-World Monkey, the Marmoset Callithrix jacchus

Journal of Neurophysiology ◽

10.1152/jn.1998.80.4.2063 ◽

1998 ◽

Vol 80 (4) ◽

pp. 2063-2076 ◽

Cited By ~ 88

Author(s):

Andrew J. R. White ◽

Heath D. Wilder ◽

Ann K. Goodchild ◽

Ann Jervie Sefton ◽

Paul R. Martin

Keyword(s):

Visual Field ◽

Receptive Field ◽

Lateral Geniculate Nucleus ◽

New World ◽

World Monkey ◽

Callithrix Jacchus ◽

Central Visual Field ◽

New World Monkey ◽

Lateral Geniculate ◽

Receptive Field Properties

White, Andrew J. R., Heath D. Wilder, Ann K. Goodchild, Ann Jervie Sefton, and Paul R. Martin. Segregation of receptive field properties in the lateral geniculate nucleus of a New-World monkey, the marmoset Callithrix jacchus. J. Neurophysiol. 80: 2063–2076, 1998. The lateral geniculate nucleus (LGN) in humans and Old-World monkeys is dominated by the representation of the fovea in the parvocellular (PC) layers, and most PC cells in the foveal representation have red–green cone opponent receptive field properties. It is not known whether these features are both unique to trichromatic primates. Here we measured receptive field properties and the visuotopic organization of cells in the LGN of a New-World monkey, the marmoset Callithrix jacchus. The marmoset displays a polymorphism of cone opsins in the medium-long wavelength (ML) range, which allows the LGN of dichromatic (“red–green color blind”) and trichromatic individuals to be compared. Furthermore, the koniocellular–interlaminar layers are segregated from the main PC layers in marmoset, allowing the functional role of this subdivision of the LGN to be assessed. We show that the representation of the visual field in the LGN is quantitatively similar in dichromatic and trichromatic marmosets and is similar to that reported for macaque; the vast majority of LGN volume is devoted to the central visual field. on- and off-type responses are partially segregated in the PC layers so that on responses are more commonly encountered near the external border of each layer. The red–green (ML) opponent cells in trichromatic animals were all located in the PC layers, and their receptive fields were within 16° of the fovea. The koniocellular zone between the PC and magnocellular layers contained cells that receive excitatory input from short wavelength sensitive cones (“blue-on cells”) as well as other nonopponent cells. These results suggest that the basic organization of the LGN is common to dichromatic and trichromatic primates and provide further evidence that ML and SWS opponent signals are carried in distinct subdivisions of the retinogeniculocortical pathway.

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Neurofilament protein expression in the geniculostriate pathway of a New World monkey (Callithrix jacchus)

Experimental Brain Research ◽

10.1007/s00221-003-1397-5 ◽

2003 ◽

Vol 150 (1) ◽

pp. 19-24 ◽

Cited By ~ 20

Author(s):

James A. Bourne ◽

Marcello G. P. Rosa

Keyword(s):

Protein Expression ◽

New World ◽

World Monkey ◽

Callithrix Jacchus ◽

Neurofilament Protein ◽

New World Monkey

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Distribution of seven major neurotransmitter receptors in the striate cortex of the new world monkey callithrix jacchus

Neuroscience ◽

10.1016/0306-4522(93)90134-2 ◽

1993 ◽

Vol 56 (4) ◽

pp. 877-885 ◽

Cited By ~ 22

Author(s):

R. Gebhard ◽

K. Zilles ◽

A. Schleicher ◽

B.J. Everitt ◽

T.W. Robbins ◽

...

Keyword(s):

New World ◽

Striate Cortex ◽

World Monkey ◽

Callithrix Jacchus ◽

Neurotransmitter Receptors ◽

New World Monkey

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The morphology and distribution of horizontal cells in the retina of a New World monkey, the marmoset Callithrix jacchus: A comparison with macaque monkey

Visual Neuroscience ◽

10.1017/s0952523800008828 ◽

1997 ◽

Vol 14 (1) ◽

pp. 125-140 ◽

Cited By ~ 18

Author(s):

Tricia L. Chan ◽

Ann K. Goodchild ◽

Paul R. Martin

Keyword(s):

New World ◽

World Monkey ◽

Macaque Monkey ◽

Callithrix Jacchus ◽

Horizontal Cells ◽

Field Size ◽

Dendritic Field ◽

Old World ◽

New World Monkey ◽

H1 Cells

AbstractThe morphology and distribution of horizontal cells was studied in the retina of a New World monkey, the marmoset, Callithrix jacchus, and compared with that of the Old World macaque monkey. Horizontal cells in macaque and marmoset were either labelled with the carbocyanine dye, Dil, and then photoconverted, or were labelled by intracellular injection with Neurobiotin. The marmoset has two types of horizontal cell, H1 and H2, which have dendritic and axonal morphology similar to their counterparts in Old World monkeys and human. The dendritic-field size of both cell types increases with distance from the fovea. Both types make contact with the vast majority of the cones within their dendritic field. The dendrites of H1 cells in marmoset contact almost twice as many cones as H1 cells in macaque at an equivalent eccentricity. With increasing distance from the fovea, H1 cells make contact with more cones but have, on average, fewer terminal knobs inserted in each cone. The increase in dendritic-field area of H1 cells is balanced by a decrease in spatial density (from 4500 cells/mm2 at 25 deg eccentricity to 1000 cells/mm2 in far peripheral retina), so coverage of the retina remains fairly constant, between 5 and 8. Overall, the results show that the qualitative morphological properties, as well as quantitative population properties of horizontal cells, are common to both New World and Old World primates.

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