Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (<i>Macropus eugenii</i>): I. Normal topography

Flett, D. L.; Marotte, L.R.; Mark, R. F.

doi:10.1002/cne.902710207

Cited by 14 publications

(8 citation statements)

References 41 publications

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“…By P94-99 discrete terminal zones are present and retinotopically aberrant axons are absent. The mature retinotopic organisation follows that of non-primate mammals: temporonasal and dorsoventral axes of the retina are represented along the rostrocaudal and lateromedial axes of the contralateral SC, respectively (Flett et al, 1988;Mark et al, 1993b) and ipsilateral projections from temporoventral retina map to rostral and primarily medial SC (Wye-Dvorak, 1984; Marotte, unpublished observations).…”

Section: Resultsmentioning

confidence: 96%

Overexpression of Ten‐m3 in the retina alters ipsilateral retinocollicular projections in the wallaby (Macropus eugenii)

Carr

Glendining

Leamey

et al. 2013

Intl J of Devlp Neuroscience

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Retinal projections to the superior colliculus are organised into retinotopic maps. Binocular vision requires that inputs from the two eyes map in register with each other. Studies in mice lacking Ten-m3, a homophilic transmembrane protein, indicate that it plays a key role in this process by influencing ipsilateral projections. The postnatal, ex utero development of the wallaby allows the targeted manipulation of molecules of interest during development. The distribution of mRNA for Ten-m3 in the retina and superior colliculus of the wallaby, and the effects of its spatiotemporally restricted retinal overexpression was investigated, in particular on the mapping of ipsilateral projections. Quantitative polymerase chain reaction found that Ten-m3 mRNA is expressed at relatively higher levels in the retina and colliculus early in development. Further, it is higher in ventral than dorsal retina, and increased in the retinotopically corresponding medial compared to lateral superior colliculus. In situ hybridisation demonstrated an increasing dorsoventral gradient in retinal ganglion cells was matched to an increasing lateromedial gradient in the superior colliculus. Overexpression of Ten-m3 by in vivo retinal electroporation produced an increase in ipsilateral projections to the binocular rostromedial colliculus, fitting with the proposal that Ten-m3 mediates mapping by attractant homophilic interactions. Retrograde labelling of the projection from this region suggested that overexpression produces a shift in the axons of existing ipsilaterally projecting ganglion cells rather than a rerouting of the axons of contralaterally projecting cells. Retinal manipulation of Ten-m3 levels produces changes in ipsilateral mapping, supporting a role for it in binocular mapping.

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Section: Resultsmentioning

confidence: 96%

Overexpression of Ten‐m3 in the retina alters ipsilateral retinocollicular projections in the wallaby (Macropus eugenii)

Carr

Glendining

Leamey

et al. 2013

Intl J of Devlp Neuroscience

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“…It is organised according to the common nonprimate plan with the temporal retina projecting rostrally, nasal retina caudally, dorsal retina laterally and ventral retina medially (Flett et al 1988;Mark et al 1993b).…”

Section: Ninety-95 Daysmentioning

confidence: 99%

Retinotopic order in the optic nerve and superior colliculus during development of the retinocollicular projection in the wallaby ( Macropus eugenii )

Ding

Marotte

1997

Anatomy and Embryology

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Retinotopic order of optic axons in the optic nerve and superior colliculus of the marsupial mammal, the wallaby (Macropus eugenii), has been examined and compared during development of the retinocollicular projection to investigate the role of order in the nerve in map formation. Small groups of axons from different retinal quadrants were labelled in vivo with a carbocyanine dye from just after axons first reached the colliculus to when the projection was mature. The distribution and branching patterns of axons and their arbors on the colliculus were assessed quantitatively during this period, as was the degree of order in the nerve. Initially, axons accumulated in coarse retinotopic order in the colliculus, with little branching and no sign of arborization to form terminal zones. Axons labelled from deposits covering a mean of 2.2% of the retina reached a mean collicular coverage of around 30% at 41-47 days, at which time they began arborizing in their retinotopically correct positions. By 55 days axons from all retinal quadrants had formed terminal zones in their retinotopically correct positions. Axons did not arborise in incorrect positions as has been reported in the rat. By 61-68 days coverage had decreased to around 10%. By 90-95 days only axons supplying terminal zones were present and terminal zones were smaller. In the nerve, axons showed a coarse and consistent order throughout development. This order was retinotopic only immediately behind the eye. Temporal and nasal axons occupied corresponding halves of the nerve along its course. Axons from dorsal and ventral retina shifted from dorsal and ventral positions in the nerve, respectively, to opposite sides of the nerve just before the chiasm. This would assist in positioning them in the appropriate lateral and medial optic tracts, respectively, in the positions they occupied as they approached the colliculus. However, the position in the nerve was not related to the ability to arborize in the correct collicular position. In particular, the increase in retinotopic order in the colliculus late in development was not accompanied by an increase in order in the nerve. Since the final organization in the colliculus shows greater order than is ever seen in the nerve, additional mechanisms must be involved in the maturation of the collicular map.

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“…Marsupial mammals like the wallaby (Macropus eugenii) show many advantages for the study of developmental neurobiological problems because the postnatally developing young are accessible at very early stages of development, in what would be foetal life in placental mammals (Mark and Marotte, 1992). The topography of the retinocollicular projection (Flett et al, 1988;Mark et al, 1993a) is the same as in other nonprimate mammals (Lund, 1978). In addition, developmental events unfold slowly compared to mammals such as the rat and mouse, thus greatly increasing the temporal resolution of developmental sequences.…”

Section: Introductionmentioning

confidence: 99%

Marsupial retinocollicular system shows differential expression of messenger RNA encoding EphA receptors and their ligands during development

Vidovic¹,

Marotte²,

Mark³

1999

J. Neurosci. Res.

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The protracted development of the wallaby (Macropus eugenii) has allowed study of messenger RNAs encoding Eph receptors EphA3 and EphA7 and ligands ephrin-A2 and -A5 in the retina and superior colliculus at intervals throughout the development of the retinocollicular projection: from birth, before retinal innervation, to postnatal day 95, when the projection is mature. Reverse transcription-polymerase chain reaction showed messenger RNAs for both receptors and ligands were expressed at all ages. EphA7 was expressed more highly in the rostral superior colliculus. Ephrin-A2 and -A5 were expressed more highly in the caudal colliculus. EphA3 was expressed in a complementary manner, more highly in temporal than in nasal retina. There are higher levels of expression of the ligands when the projection is only coarsely topographically organised. This suggests a role for them and their receptor EphA3 in this stage, by repulsive interactions which restrict temporal axons to rostral superior colliculus. This is the first account in a marsupial mammal of the appearance of this molecular family, substantiating its ubiquitous role in topographically organised neuronal connections. Nevertheless, expression is not the same as in the mouse, suggesting differences in the details of topographic coding between species.

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Retinal projections to the superior colliculus and dorsal lateral geniculate nucleus in the tammar wallaby (Macropus eugenii): I. Normal topography

Cited by 14 publications

References 41 publications

Overexpression of Ten‐m3 in the retina alters ipsilateral retinocollicular projections in the wallaby (Macropus eugenii)

Overexpression of Ten‐m3 in the retina alters ipsilateral retinocollicular projections in the wallaby (Macropus eugenii)

Retinotopic order in the optic nerve and superior colliculus during development of the retinocollicular projection in the wallaby ( Macropus eugenii )

Marsupial retinocollicular system shows differential expression of messenger RNA encoding EphA receptors and their ligands during development

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