Tetsuya Togano

Identification of functional marker proteins in the mammalian growth cone

Identification of proteins in the mammalian growth cone has the potential to advance our understanding of this critical regulator of neuronal growth and formation of neural circuit; however, to date, only one growth cone marker protein, GAP-43, has been reported. Here, we successfully used a proteomic approach to identify 945 proteins present in developing rat forebrain growth cones, including highly abundant, membrane-associated and actin-associated proteins. Almost 100 of the proteins appear to be highly enriched in the growth cone, as determined by quantitative immunostaining, and for 17 proteins, the results of RNAi suggest a role in axon growth. Most of the proteins we identified have not previously been implicated in axon growth and thus their identification presents a significant step forward, providing marker proteins and candidate neuronal growth-associated proteins.

Topically administered timolol and dorzolamide reduce intraocular pressure and protect retinal ganglion cells in a rat experimental glaucoma model

Aims: This study sought to elucidate the effects of timolol and dorzolamide on intraocular pressure (IOP) and retinal ganglion cell (RGC) death in an experimental model of glaucoma in rat. Methods: Mild elevation of IOP was induced in rats by intracameral injection of India ink and subsequent laser trabecular photocoagulation. IOP was measured before the surgical procedures and weekly thereafter. Timolol (0.5%), timolol XE (0.5%), dorzolamide (1%), and artificial tears (vehicle) were topically applied daily. Retinal sections were prepared for histology to determine RGC number. Results: Timolol, timolol XE, and dorzolamide induced a significant reduction in IOP (p<0.05) and counteracted the reduction in RGC number that occurred in vehicle treated glaucomatous eyes (p<0.05). The coefficient of correlation between RGC number and IOP was significant in the dorzolamide treated group (r = −0.908, p<0.005), but not in other groups (p>0.05). Conclusions: Both timolol formulation and dorzolamide reduced IOP and protected RGCs in a rat model of experimental glaucoma. It cannot be ruled out that timolol might protect RGCs by additional mechanisms other than simply lowering of IOP.

Progression rate of total, and upper and lower visual field defects in open-angle glaucoma patients

Purpose We evaluated the progression rate of total, and upper and lower visual field defects in treated open-angle glaucoma patients. Patients and methods This study was a retrospective, nonrandomized, comparative study. Five-hundred forty-four eyes from 315 Japanese open-angle glaucoma patients were examined. The mean deviation (MD) and total deviation (TD) for both the upper and lower slopes on the Humphrey Field Analyzer were calculated and compared in high-tension glaucoma (>21 mmHg) and normal-tension glaucoma (≤21 mmHg). Results Patients with over −20 dB of MD and over −23 dB of upper or lower TD were enrolled into each analysis. Patients with −7.75 ± 5.30 (mean ± standard deviation) dB of MD, −9.16 ± 10.80 dB of upper TD, or −7.11 ± 6.02 dB of lower TD were followed up for 4–19 years. The mean MD slope was −0.41 ± 0.50 dB/year, the upper TD slope was −0.46 ± 0.65 dB/year, and the lower TD slope was −0.32 ± 0.53 dB/year. Comparing high-tension glaucoma and normal-tension glaucoma, the upper TD slope was similar for both types of glaucoma, but the MD and lower TD slopes in high-tension glaucoma were significantly lower than those in normal-tension glaucoma. Conclusions The progression rates in lower visual field defects in high-tension glaucoma might be faster than those in normal-tension glaucoma. The results of this study might be used to predict the prognosis of visual field defects, as well as the quality of vision in patients with open-angle glaucoma.

Role of Ser50 phosphorylation in SCG10 regulation of microtubule depolymerization

Members of the stathmin‐like protein family depolymerize microtubules (MTs), probably due to the ability of each stathmin monomer to bind two tubulin heterodimers in a complex (T2S complex). SCG10, a member of this family, is localized in the growth cone of neurons. It has four identified sites of serine phosphorylation (S50, S63, S73, and S97). Of these, S50 and S97 are phosphorylated by cAMP‐dependent protein kinase, an enzyme involved in growth cone guidance. When the equivalent sites in stathmins are phosphorylated, they lose their ability to depolymerize MTs. We investigated the specific role of the two cAMP‐dependent protein kinase (PKA) phosphorylation sites in SCG10. A mutant of SCG10 phosphorylated only on S50 retained the ability to depolymerize MTs, but SCG10 phosphorylated on S97 or on both S50 and S97 lost MT‐depolymerizing activity. Surface plasmon resonance studies revealed that the phosphorylation of SCG10 at these sites reduced the tubulin heterodimer binding, mainly due to a reduced rate of association. In particular, compared to the two other phosphorylated forms, SCG10 phosphorylated at S50 had a significantly smaller dissociation constant for the binding of the first tubulin heterodimer and larger association and dissociation rate constants for the binding of the second heterodimer. This indicates that the phosphorylation of S50 compensates for the effect of phosphorylation at other sites by modulating T2S complex formation. Furthermore, these results suggest that S50‐P maintains MT‐depolymerizing activity, which indicates that the biological functions of phosphorylation at S50 and S97 are different.

The Relationship Between the Mean Deviation Slope and Follow-up Intraocular Pressure in Open-angle Glaucoma Patients

Purpose:The purpose of this study was to analyze the relationship between the mean deviation (MD) slope as the progressive rate of visual field defects and the follow-up intraocular pressure (IOP) in open-angle glaucoma (OAG) patients. Methods:This study was a retrospective, nonrandomized comparative study. A total of 287 eyes from 287 Japanese OAG patients were examined. The MD slope of the Humphrey Field Analyzer was calculated and compared with the follow-up IOP. OAG was classified into the high-tension group (>21 mm Hg) and the normal-tension group (⩽21 mm Hg) on the basis of the highest recorded IOP without treatment, and then the 2 groups were compared. After setting a threshold for the progression rate at −0.3 dB/y, related factors were compared between the fast-progression and slow-progression eyes in each group. Results:The correlation line between the follow-up IOP and the MD slope was statistically significant in the high-tension group but not in the normal-tension group. Compared with eyes with slow progression, eyes with fast progression in the high-tension group were older and had a higher mean IOP, greater highest and lowest IOPs, and a smaller mean IOP reduction ratio, whereas eyes with fast progression in the normal-tension group had a greater SD of the mean IOP, a larger IOP range, and a greater highest IOP. Conclusions:Eyes with a faster visual field progression tended to have a higher follow-up IOP in the high-tension group and larger IOP fluctuations in the normal-tension group of OAG patients. We should monitor both the follow-up IOP and fluctuations in IOP to provide a safer and more reliable visual field prognosis for OAG.

Point Mutation in Syntaxin-1A Causes Abnormal Vesicle Recycling, Behaviors, and Short Term Plasticity

Background: Roles of the syntaxin-1A·CaMKII interaction are not physiologically understood in vivo. Results: A point mutation in syntaxin-1A caused abnormal plasticity, recycling, and behaviors in mice. Conclusion: The CaMKII/syntaxin-1A interaction is essential for maintenance of neuronal plasticity. Significance: Syntaxin-1A is involved in regulatory pathways in higher brain functions. Syntaxin-1A is a t-SNARE that is involved in vesicle docking and vesicle fusion; it is important in presynaptic exocytosis in neurons because it interacts with many regulatory proteins. Previously, we found the following: 1) that autophosphorylated Ca2+/calmodulin-dependent protein kinase II (CaMKII), an important modulator of neural plasticity, interacts with syntaxin-1A to regulate exocytosis, and 2) that a syntaxin missense mutation (R151G) attenuated this interaction. To determine more precisely the physiological importance of this interaction between CaMKII and syntaxin, we generated mice with a knock-in (KI) syntaxin-1A (R151G) mutation. Complexin is a molecular clamp involved in exocytosis, and in the KI mice, recruitment of complexin to the SNARE complex was reduced because of an abnormal CaMKII/syntaxin interaction. Nevertheless, SNARE complex formation was not inhibited, and consequently, basal neurotransmission was normal. However, the KI mice did exhibit more enhanced presynaptic plasticity than wild-type littermates; this enhanced plasticity could be associated with synaptic response than did wild-type littermates; this pronounced response included several behavioral abnormalities. Notably, the R151G phenotypes were generally similar to previously reported CaMKII mutant phenotypes. Additionally, synaptic recycling in these KI mice was delayed, and the density of synaptic vesicles was reduced. Taken together, our results indicated that this single point mutation in syntaxin-1A causes abnormal regulation of neuronal plasticity and vesicle recycling and that the affected syntaxin-1A/CaMKII interaction is essential for normal brain and synaptic functions in vivo.

Nanophthalmos: quantitative analysis of anterior chamber angle configuration before and after cataract surgery

Background/aims To analyse quantitatively the anterior segment configuration in eyes with nanophthalmos before and after cataract surgery. Methods This was a retrospective, non-comparative, interventional case series. Eleven eyes in eight patients with nanophthalmos who underwent phacoemulsification and intraocular lens implantation were identified from the departments surgical log, and their clinical records were retrospectively reviewed. Main outcome measures were as follows: visual acuity, intraocular pressure (IOP), axial length and the following ultrasound biomicroscopy parameters: angle opening distance at 500 μm anterior to the scleral spur (AOD500), trabecular–iris angle (TIA) and trabecular ciliary process distance. Results The mean axial length of the eyes was 17.3±1.7 mm. AOD500 and TIA increased after cataract surgery (p<0.005). Smaller axial length, AOD500 and TIA before cataract surgery were observed in eyes with preoperative IOP elevation than those without preoperative IOP elevation (p<0.05). Lower postoperative IOP was correlated with greater AOD500 and TIA before cataract surgery (p<0.05). Conclusions Cataract surgery deepened the anterior chamber and widened the anterior chamber angle in nanophthalmic eyes. Cataract surgery may have beneficial effects on IOP in eyes with nanophthalmos.

Clinical evaluation of microcystic macular edema in patients with glaucoma

PurposeTo investigate the prevalence of microcystic macular edema (MME) in patients with glaucoma and the relationship between glaucomatous visual field defects and MME.Patients and methodsWe analyzed 636 eyes of 341 glaucoma patients who underwent spectral domain optical coherence tomography (SD-OCT). MME was defined as vacuoles observed in the inner nuclear layer (INL) on SD-OCT. Quantitative assessment of MME area was performed using en-face imaging obtained swept-source OCT (SS-OCT) and Adobe Photoshop CS6 Extended software. These values were compared with the visual field results with the Humphrey field analyzer.ResultsMME was observed in 1.6% of eyes. The visual field mean deviation (MD), pattern standard deviation (PSD) and visual acuity was significantly worse (P= 0.023, P=0.037, and P=0.018, respectively) in eyes with MME. The average MME area was 2.38±1.43%. There was no significant correlation between visual field deficits and MME area.ConclusionsThe MME detection rate based on general inspection was 1.6%. MME in glaucomatous eyes were associated with worse MD, PSD, and visual acuity. Further research is needed to increase the number of cases to allow for more detailed analysis.

Effect on intraocular pressure of switching from latanoprost and travoprost monotherapy to timolol fixed combinations in patients with normal-tension glaucoma.

Purpose. To evaluate the effect on intraocular pressure (IOP) of switching from latanoprost and travoprost monotherapy to timolol fixed combinations in Japanese patients with normal-tension glaucoma (NTG). Methods. 27 NTG patients (54 eyes) were compared IOP, superficial punctuate keratitis (SPK) scores, and conjunctival injection scores in eyes treated with prostaglandin (PG) or PG analog/beta-blocker (PG/b) fixed-combination 6 months after the change in therapy. Results. The mean baseline intraocular pressure was 17.4 ± 1.59 mmHg in eyes receiving PG therapy only and 17.4 ± 1.69 mmHg in eyes switched to PG/b. Switching to fixed combination therapy from PG monotherapy, the mean IOP was 13.1 ± 1.79 mmHg (P < 0.001)  (−24.71% reduction from baseline) at 6 months. The mean conjunctival injection score was 0.69 for eyes on PG monotherapy and 0.56 for eyes on fixed combination therapy (P = 0.028). The mean SPK scores were 0.46 and 0.53. This difference was not statistically significant (P = 0.463). Conclusions. Switching from PG monotherapy to PG/b fixed combination therapy for NTG resulted in a greater intraocular pressure reduction than PG alone without increasing the number of instillations.

[Persistent hyperplastic primary vitreous--a case report of adult onset acute angle-closure glaucoma].

BACKGROUND We report a patient with persistent hyperplastic primary vitreous(PHPV) who presented with acute angle-closure glaucoma in his adult life. CASE A 30-year-old man had an attack of acute angle-closure glaucoma associated with retrolenticular fibrous tissue, atrophic retina, and elongated cilliary process in his right eye. RESULT Ultrasound biomicroscopy(UBM) study showed iris bowing, shallow anterior chamber, and elongated cilliary body which were being pulled by the retrolenticular mass. The posterior chamber was normal. CONCLUSION Although the mechanisms of secondary angle-closure glaucoma in PHPV are complicated, we suspected pupillary block resulting from constriction by the retrolenticular mass in this case.