Identification of Retinal Ganglion Cells and Their Projections Involved in Central Transmission of Information about Upward and Downward Image Motion

The direction of image motion is coded by direction-selective (DS) ganglion cells in the retina. Particularly, the ON DS ganglion cells project their axons specifically to terminal nuclei of the accessory optic system (AOS) responsible for optokinetic reflex (OKR). We recently generated a knock-in mouse in which SPIG1 (SPARC-related protein containing immunoglobulin domains 1)-expressing cells are visualized with GFP, and found that retinal ganglion cells projecting to the medial terminal nucleus (MTN), the principal nucleus of the AOS, are comprised of SPIG1+ and SPIG1− ganglion cells distributed in distinct mosaic patterns in the retina. Here we examined light responses of these two subtypes of MTN-projecting cells by targeted electrophysiological recordings. SPIG1+ and SPIG1− ganglion cells respond preferentially to upward motion and downward motion, respectively, in the visual field. The direction selectivity of SPIG1+ ganglion cells develops normally in dark-reared mice. The MTN neurons are activated by optokinetic stimuli only of the vertical motion as shown by Fos expression analysis. Combination of genetic labeling and conventional retrograde labeling revealed that axons of SPIG1+ and SPIG1− ganglion cells project to the MTN via different pathways. The axon terminals of the two subtypes are organized into discrete clusters in the MTN. These results suggest that information about upward and downward image motion transmitted by distinct ON DS cells is separately processed in the MTN, if not independently. Our findings provide insights into the neural mechanisms of OKR, how information about the direction of image motion is deciphered by the AOS

A distinct effect of transient and sustained upregulation of cellular factor XIII in the goldfish retina and optic nerve on optic nerve regeneration

Unlike in mammals, fish retinal ganglion cells (RGCs) have a capacity to repair their axons even after optic nerve transection. In our previous study, we isolated a tissue type transglutaminase (TG) from axotomized goldfish retina. The levels of retinal TG (TG R) mRNA increased in RGCs 1-6 weeks after nerve injury to promote optic nerve regeneration both in vitro and in vivo. In the present study, we screened other types of TG using specific FITC-labeled substrate peptides to elucidate the implications for optic nerve regeneration. This screening showed that the activity of only cellular coagulation factor XIII (cFXIII) was increased in goldfish optic nerves just after nerve injury. We therefore cloned a full-length cDNA clone of FXIII A subunit (FXIII-A) and studied temporal changes of FXIII-A expression in goldfish optic nerve and retina during regeneration. FXIII-A mRNA was initially detected at the crush site of the optic nerve 1 h after injury; it was further observed in the optic nerve and achieved sustained long-term expression (1-40 days after nerve injury). The cells producing FXIII-A were astrocytes/microglial cells in the optic nerve. By contrast, the expression of FXIII-A mRNA and protein was upregulated in RGCs for a shorter time (3-10 days after nerve injury). Overexpression of FXIII-A in RGCs achieved by lipofection induced significant neurite outgrowth from unprimed retina, but not from primed retina with pretreatment of nerve injury. Addition of extracts of optic nerves with injury induced significant neurite outgrowth from primed retina, but not from unprimed retina without pretreatment of nerve injury. The transient increase of cFXIII in RGCs promotes neurite sprouting from injured RGCs, whereas the sustained increase of cFXIII in optic nerves facilitates neurite elongation from regrowing axons. © 2012 Elsevier Ltd. All rights reserved

Expression of SPIG1 Reveals Development of a Retinal Ganglion Cell Subtype Projecting to the Medial Terminal Nucleus in the Mouse

Visual information is transmitted to the brain by roughly a dozen distinct types of retinal ganglion cells (RGCs) defined by a characteristic morphology, physiology, and central projections. However, our understanding about how these parallel pathways develop is still in its infancy, because few molecular markers corresponding to individual RGC types are available. Previously, we reported a secretory protein, SPIG1 (clone name; D/Bsp120I #1), preferentially expressed in the dorsal region in the developing chick retina. Here, we generated knock-in mice to visualize SPIG1-expressing cells with green fluorescent protein. We found that the mouse retina is subdivided into two distinct domains for SPIG1 expression and SPIG1 effectively marks a unique subtype of the retinal ganglion cells during the neonatal period. SPIG1-positive RGCs in the dorsotemporal domain project to the dorsal lateral geniculate nucleus (dLGN), superior colliculus, and accessory optic system (AOS). In contrast, in the remaining region, here named the pan-ventronasal domain, SPIG1-positive cells form a regular mosaic and project exclusively to the medial terminal nucleus (MTN) of the AOS that mediates the optokinetic nystagmus as early as P1. Their dendrites costratify with ON cholinergic amacrine strata in the inner plexiform layer as early as P3. These findings suggest that these SPIG1-positive cells are the ON direction selective ganglion cells (DSGCs). Moreover, the MTN-projecting cells in the pan-ventronasal domain are apparently composed of two distinct but interdependent regular mosaics depending on the presence or absence of SPIG1, indicating that they comprise two functionally distinct subtypes of the ON DSGCs. The formation of the regular mosaic appears to be commenced at the end of the prenatal stage and completed through the peak period of the cell death at P6. SPIG1 will thus serve as a useful molecular marker for future studies on the development and function of ON DSGCs

Enriched Expression of Serotonin 1B and 2A Receptor Genes in Macaque Visual Cortex and their Bidirectional Modulatory Effects on Neuronal Responses

To study the molecular mechanism how cortical areas are specialized in adult primates, we searched for area-specific genes in macaque monkeys and found striking enrichment of serotonin (5-hydroxytryptamine, 5-HT) 1B receptor mRNA, and to a lesser extent, of 5-HT2A receptor mRNA, in the primary visual area (V1). In situ hybridization analyses revealed that both mRNA species were highly concentrated in the geniculorecipient layers IVA and IVC, where they were coexpressed in the same neurons. Monocular inactivation by tetrodotoxin injection resulted in a strong and rapid (<3 h) downregulation of these mRNAs, suggesting the retinal activity dependency of their expression. Consistent with the high expression level in V1, clear modulatory effects of 5-HT1B and 5-HT2A receptor agonists on the responses of V1 neurons were observed in in vivo electrophysiological experiments. The modulatory effect of the 5-HT1B agonist was dependent on the firing rate of the recorded neurons: The effect tended to be facilitative for neurons with a high firing rate, and suppressive for those with a low firing rate. The 5-HT2A agonist showed opposite effects. These results suggest that this serotonergic system controls the visual response in V1 for optimization of information processing toward the incoming visual inputs

A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan

Shintani, Aki, Umemura, Shinya, Nakano, Takafumi, Tomikawa, Ko (2023): A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan. Zootaxa 5301 (3): 383-396, DOI: 10.11646/zootaxa.5301.3.4, URL: http://dx.doi.org/10.11646/zootaxa.5301.3.

FIGURE 4 in A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan

FIGURE 4. Pseudocrangonys asuwaensis sp. nov. holotype female (KUZ Z4464), 5.4 mm, Nanatsuoguchi, Mt. Asuwa, Fukui, Japan. A, pereopod 3, lateral view; B, dactylus of pereopod 3, lateral view; C–F, pereopods 4–7, lateral views.Published as part of Shintani, Aki, Umemura, Shinya, Nakano, Takafumi & Tomikawa, Ko, 2023, A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan, pp. 383-396 in Zootaxa 5301 (3) on page 388, DOI: 10.11646/zootaxa.5301.3.4, http://zenodo.org/record/803054

FIGURE 3 in A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan

FIGURE 3. Pseudocrangonys asuwaensis sp. nov. holotype female (KUZ Z4464), 5.4 mm, Nanatsuoguchi, Mt. Asuwa, Fukui, Japan. A, maxilliped, dorsal view; B, inner plate of maxilliped, dorsal view; C, outer plate of maxilliped, dorsal view; D, gnathopod 1, medial view; E, palmar margin of propodus and dactylus of gnathopod 1, medial view; F, gnathopod 2, medial view; G, palmar margin of propodus and dactylus of gnathopod 2, medial view; H, brood plate of gnathopod 2, lateral view.Published as part of &lt;i&gt;Shintani, Aki, Umemura, Shinya, Nakano, Takafumi &amp; Tomikawa, Ko, 2023, A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan, pp. 383-396 in Zootaxa 5301 (3)&lt;/i&gt; on page 387, DOI: 10.11646/zootaxa.5301.3.4, &lt;a href="http://zenodo.org/record/8030542"&gt;http://zenodo.org/record/8030542&lt;/a&gt

Substrate Specificity of R3 Receptor-like Protein-tyrosine Phosphatase Subfamily toward Receptor Protein-tyrosine Kinases

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FIGURE 1 in A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan

FIGURE 1. Habitat and live specimen of Pseudocrangonys asuwaensis sp. nov. A, entrance of Nanatsuoguchi, Mt. Asuwa, Fukui, Japan; B, female (about 6 mm in body length).Published as part of &lt;i&gt;Shintani, Aki, Umemura, Shinya, Nakano, Takafumi &amp; Tomikawa, Ko, 2023, A new species of the genus Pseudocrangonyx (Crustacea: Amphipoda: Pseudocrangonyctidae) from subterranean waters of Japan, pp. 383-396 in Zootaxa 5301 (3)&lt;/i&gt; on page 385, DOI: 10.11646/zootaxa.5301.3.4, &lt;a href="http://zenodo.org/record/8030542"&gt;http://zenodo.org/record/8030542&lt;/a&gt