[Research progress of metal micro-battery dressings in wound repair]

To develop the dressings that can both inhibit bacterial infection and actively promote healing is of great importance for wound repair and the development of medical technology. Electrical stimulation has multiple roles in wound healing, including hemostasis, antibacterial, anti-inflammatory, guidance of cell migration, promotion of re-epithelialization, and proliferation of cells. Metal micro-battery can provide a stable source of electrical stimulation energy without an external power source. Thus, the integration of metal micro-battery with medical dressings opens up new opportunities for the wireless application of electrical stimulation in wound repair. In this review, the mechanism of the effect of electrical stimulation on wound healing is systematically presented, then recent advances in metal micro-battery dressings, including preparation methods, antibacterial performance, and healing properties are mainly introduced, and the current challenges and prospects of metal micro-battery dressings are also provided.

Study protocol: a multicentre, prospective, phase II trial of isotoxic hypofractionated concurrent chemoradiotherapy for non-small cell lung cancer

INTRODUCTION

Concurrent chemoradiotherapy with conventional fractionation has been acknowledged as one of the standard treatments for locally advanced non-small cell lung cancer (NSCLC). The radiotherapy dose of 60 Gy is far from enough for local tumour control. Due to this fact, hypofractionated radiotherapy can shorten the total treatment duration, partially counteract the accelerated repopulation of tumour cells and deliver a higher biological effective dose, it has been increasingly used for NSCLC. In theory, concurrent hypofractionated chemoradiotherapy can result in an enhanced curative effect. To date, the vast majority of radiotherapy prescriptions assign a uniform radiotherapy dose to all patients. However this kind of uniform radiotherapy prescription may lead to two consequences: excess damage to normal tissues for large tumours and insufficient dose for small tumours. Our study aims to evaluate whether delivering individualised radiotherapy dose is feasible using intensity-modulated radiotherapy.

METHODS AND ANALYSIS

Our study of individualised radiotherapy is a multicenter phase II trial. From April 2019, a total of 30 patients from three Chinese centres, with a proven histological or cytological diagnosis of inoperable NSCLC, will be recruited. The dose of radiation will be increased until one or more of the organs at risk tolerance or the maximum dose of 69 Gy is reached. The primary end point is feasibility, with response rates, progression-free survival and overall survival as secondary end points. The concurrent chemotherapy regimen will be docetaxel plus lobaplatin.

ETHICS AND DISSEMINATION

The study has been approved by medical ethics committees from three research centres. The trial is conducted in accordance with the Declaration of Helsinki.The trial results will be disseminated through academic conference presentations and peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT03606239.

Cryoablation combined with radiotherapy for hepatic malignancy: Five case reports

BACKGROUND

The survival of patients treated with monotherapy for hepatic malignancies is not ideal. A comprehensive program of cryoablation combined with radiotherapy for the treatment of hepatic malignancies results in less trauma to the patients. It may provide an option for the treatment of patients with advanced hepatic malignancies.

CASE SUMMARY

We reported 5 cases of advanced-stage hepatic malignancies treated in our hospital from 2017-2018, including 3 cases of primary hepatocellular carcinoma and 2 cases of metastatic hepatic carcinoma. They first received cryoablation therapy on their liver lesions. The procedure consisted of 2 freeze-thaw cycles, and for each session, the duration of freezing was 13-15 min, and the natural re-warming period was 2-8 min. Depending on the tumor size, the appropriate cryoprobes were selected to achieve complete tumor ablation to the greatest extent possible. After cryoablation surgery, intensity-modulated radiotherapy (IMRT) for liver lesions was performed, and the radiotherapy regimen was 5400 cGy/18f and 300 cGy/f. None of the 5 patients had adverse events above grade II, and their quality of life was significantly improved. Among them, 4 patients were free of disease progression in the liver lesions under local control, and their survival was prolonged; 3 patients are still alive.

CONCLUSION

Our clinical practice demonstrated that cryoablation combined with IMRT could be implemented safely. The definitive efficacy for hepatic malignancies needs to be confirmed in larger-size sample prospective studies.

High-intensity focused ultrasound combined with transcatheter arterial chemoembolization and radiotherapy for advanced hepatocellular carcinoma: A case report

INTRODUCTION

Primary hepatocellular carcinoma (HCC) is one of the most common malignancies, only 10% to 20% of HCC patients are surgically resectable as most of the patients are diagnosed at advanced stages at presentation. The efficiencies of transcatheter arterial chemoembolization (TACE), high-intensity focused ultrasound (HIFU), and three-dimensional conformal radiation therapy (3D-CRT) in patients with advanced HCC have been clinically confirmed. We here report a patient with HCC accompanied by venous tumor thrombus, who was treated with the combination of these 3 therapies. The patient survived for 16 months with good quality of life.

PATIENT CONCERNS

The patient was a 72-year-old male with a primary multicentric HCC accompanied by tumor thrombus in the right hepatic vein. The patient had the symptoms of abdominal distention and liver pain. He refused sorafenib treatment because of personal reason.

DIAGNOSIS

Primary multicentric HCC stage IIIB cT4N0M0, accompanied by tumor thrombus in the right hepatic vein; chronic viral hepatitis B; and hepatitis B virus-related decompensated liver cirrhosis.

INTERVENTIONS

TACE + HIFU + 3D-CRT.

OUTCOMES

The patient had an overall survival of 16 months with good quality of life. Compared with monotherapy, the combined therapy significantly prolonged patient survival time with improved clinical benefits.

CONCLUSION

The combination of TACE, HIFU, and 3D-CRT is safe and effective in the treatment of advanced HCC, which provides a possible comprehensive treatment strategy for advanced HCC.

Progress in image-guided radiotherapy for the treatment of non-small cell lung cancer

Lung cancer is one of the most common malignant tumors. It has the highest incidence and mortality rate of all cancers worldwide. Late diagnosis of non-small cell lung cancer (NSCLC) is very common in clinical practice, and most patients miss the chance for radical surgery. Thus, radiotherapy plays an indispensable role in the treatment of NSCLC. Radiotherapy technology has evolved from the classic two-dimensional approach to three-dimensional conformal and intensity-modulated radiotherapy. However, how to ensure delivery of an accurate dose to the tumor while minimizing the irradiation of normal tissues remains a huge challenge for radiation oncologists, especially due to the positioning error between fractions and the autonomous movement of organs. In recent years, image-guided radiotherapy (IGRT) has greatly increased the accuracy of tumor irradiation while reducing the irradiation dose delivered to healthy tissues and organs. This paper presents a brief review of the definition of IGRT and the various technologies and applications of IGRT. IGRT can help ensure accurate dosing of the target area and reduce radiation damage to the surrounding normal tissue. IGRT may increase the local control rate of tumors and reduce the incidence of radio-therapeutic complications.

[Association of sleep-disorders with systemic inflammatory markers and acute exacerbation in chronic obstructive pulmonary disease patients]

Objective: To investigate the association of sleep quality with the levels of systemic inflammatory markers in patients with chronic obstructive pulmonary disease(COPD) and the correlations between the frequency of acute exacerbation of COPD (AECOPD) and Pittsburgh sleep quality index (PSQI). Methods: A total of 198 COPD patients admitted in our hospital from October, 2016 to June, 2017 were screened, and 124 patients were eligible for the study. On the first day of hospitalization, the serum samples and clinical data were collected, including white blood cells, lymphocytes, platelet count, CRP and PSQI. Poor sleep quality was defined as PSQI score >5. Results: The percentage of COPD patients with poor sleep quality was about 68%. Poor sleep quality was positively correlated with the frequency of acute exacerbation in COPD patients. The ratio of neutrophil to lymphocyte (NLR), ratio of platelet to lymphocyte (PLR) and levels of CRP were higher in patients with poor sleep quality than those in the control group. NLR, PLR and CRP in peripheral blood of the patients with poor sleep quality were positively correlated with PSQI score. The CRP levels and PSQI score in COPD patients with poor sleep quality group were positively correlated with the frequency of exacerbations in the past year (r=0.437, r=0.430). Conclusion: A high percentage of COPD patients had poor sleep quality, which was positively correlated with the levels of systemic inflammation as well as the frequency of AECOPD.

Mandibular symphyseal midline distraction osteogenesis for micrognathia associated with aglossia and situs inversus totalis

Aglossia is a rare congenital abnormality, often associated with micrognathia and limb defects. Situs inversus totalis is also a rare congenital abnormality, defined as a mirror-image reversal of all the asymmetric organs of the thorax and abdomen. The concurrence of these two abnormalities has only been reported in eight similar cases in the literature. Although micrognathia and malocclusion were observed in all of these cases, few treatments were performed for the patients' dentofacial deformities. This report describes the case of a 7-year-old boy suffering from micrognathia, aglossia, and situs inversus totalis simultaneously, and the treatment for his micrognathia by mandibular symphyseal midline distraction osteogenesis, guided by virtual surgical planning and a three-dimensional printed surgical template. In a review of the literature, this is the first case of micrognathia associated with aglossia and situs inversus totalis that has been treated by mandibular symphyseal midline distraction osteogenesis for the dentofacial deformity.

miRNA and piRNA expression profiles of breeder cock testes detected by next-generation sequencing

miRNAs are small non-coding regulatory RNAs that play key roles in diverse biological processes. In this study, we used the Solexa sequencing technique to profile miRNAs in breeder cock testes to illustrate their functions. A total of 663 co-expressed miRNAs and 3,180 co-expressed piRNAs were detected in three libraries. Based on Mir-X^™ miRNA qRT-PCR, three miRNAs representing low, medium and high expression levels according to the sequencing results were selected randomly to validate the miRNAs' expression profiles. Results suggested that the miRNA expression profiles data could represent actual miRNA expression levels. Moreover, target genes prediction of the co-expressed miRNAs and further Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed, which revealed that some candidate miRNAs were involved in the regulation of the spermatogenesis process, spermatozoa function and testicular metabolism. In conclusion, we provided a useful resource for further elucidation of the miRNAs' regulatory role in spermatogenesis, contributing to a preliminary database for functional and molecular mechanistic studies in testicular metabolism, spermatogenesis and other testes functions.

Accelerated hypofractionated three-dimensional conformal radiation therapy (3 Gy/fraction) combined with concurrent chemotherapy for patients with unresectable stage III non-small cell lung cancer: preliminary results of an early terminated phase II trial

BACKGROUND

Increasing the biological effective dose (BED) of radiotherapy for non-small cell lung cancer (NSCLC) can increase local control rates and improve overall survival. Compared with conventional fractionated radiotherapy, accelerated hypofractionated radiotherapy can yield higher BED, shorten the total treatment time, and theoretically obtain better efficacy. However, currently, there is no optimal hypofractionated radiotherapy regimen. Based on phase I trial results, we performed this phase II trial to further evaluate the safety and preliminary efficacy of accelerated hypofractionated three-dimensional conformal radiation therapy(3-DCRT) combined with concurrent chemotherapy for patients with unresectable stage III NSCLC.

METHODS

Patients with previously untreated unresectable stage III NSCLC received 3-DCRT with a total dose of 69 Gy, delivered at 3 Gy per fraction, once daily, five fractions per week, completed within 4.6 weeks. At the same time, platinum doublet chemotherapy was applied.

RESULTS

After 12 patients were enrolled in the group, the trial was terminated early. There were five cases of grade III radiation esophagitis, of which four cases completed the radiation doses of 51 Gy, 51 Gy, 54 Gy, and 66 Gy, and one case had 16 days of radiation interruption. The incidence of grade III acute esophagitis in patients receiving an irradiation dose per fraction ≥2.7 Gy on the esophagus was 83.3% (5/6). The incidence of symptomatic grade III radiation pneumonitis among the seven patients who completed 69 Gy according to the plan was 28.6% (2/7). The median local control (LC) and overall survival (OS) were not achieved; the 1-year LC rate was 59.3%, and the 1-year OS rate was 78.6%.

CONCLUSION

For unresectable stage III NSCLC, the accelerated hypofractionated radiotherapy with a total dose of 69 Gy (3 Gy/f) combined with concurrent chemotherapy might result in severe radiation esophagitis and pneumonitis to severely affect the completion of the radiotherapy. Therefore, we considered that this regimen was infeasible. During the hypofractionated radiotherapy with concurrent chemotherapy, the irradiation dose per fraction to esophagus should be lower than 2.7 Gy. Further studies should be performed using esophageal tolerance as a metric in dose escalation protocols.

TRIAL REGISTRATION

NCT02720614, the date of registration: March 23, 2016.

Treating advanced non-small-cell lung cancer in Chinese patients: focus on icotinib

Icotinib hydrochloride is an orally administered small-molecule reversible tyrosine kinase inhibitor that has been independently researched and developed and has independent intellectual property rights in the People's Republic of China. Clinical trials have demonstrated that the response to icotinib among advanced non-small-cell lung cancer (NSCLC) patients who received at least one platinum-based chemotherapy regimen was not inferior to gefitinib. Since being launched August 2011 in the People's Republic of China, icotinib has been widely used in clinics, and has become an important treatment option for Chinese patients with advanced NSCLC. The present study presents the Phase I, II, and III clinical trials of icotinib and discusses current clinical applications in the People's Republic of China and future research directions.

Regulation of autophagy by miR-30d impacts sensitivity of anaplastic thyroid carcinoma to cisplatin

miR-30d has been observed to be significantly down-regulated in human anaplastic thyroid carcinoma (ATC), and is believed to be an important event in thyroid cell transformation. In this study, we found that miR-30d has a critical role in modulating sensitivity of ATC cells to cisplatin, a commonly used chemotherapeutic drug for treatment of this neoplasm. Using a mimic of miR-30d, we demonstrated that miR-30d could negatively regulate the expression of beclin 1, a key autophagy gene, leading to suppression of the cisplatin-activated autophagic response that protects ATC cells from apoptosis. A reporter gene assay demonstrated that the binding sequences of miR-30d in the beclin 1-3' UTR was the region required for the inhibition of beclin 1 expression by this miRNA. We further showed that inhibition of the beclin 1-mediated autophagy by the miR-30d mimic sensitized ATC cells to cisplatin both in vitro (cell culture) and in vivo (animal xenograft model). These results suggest that dysregulation of miR-30d in ATC cells is responsible for the insensitivity to cisplatin by promoting autophagic survival. Thus, miR-30d may be exploited as a potential target for therapeutic intervention in the treatment of ATC.

Phase II clinical trial of whole-brain irradiation plus three-dimensional conformal boost with concurrent topotecan for brain metastases from lung cancer

BACKGROUND

Patients with brain metastases from lung cancer have poor prognoses and short survival time, and they are often excluded from clinical trials. Whole-cranial irradiation is considered to be the standard treatment, but its efficacy is not satisfactory. The purpose of this phase II clinical trial was to evaluate the preliminary efficacy and safety of the treatment of whole-brain irradiation plus three-dimensional conformal boost combined with concurrent topotecan for the patients with brain metastases from lung cancer.

METHODS

Patients with brain metastasis from lung cancer received concurrent chemotherapy and radiotherapy: conventional fractionated whole-brain irradiation, 2 fields/time, 1 fraction/day, 2 Gy/fraction, 5 times/week, and DT 40 Gy/20 fractions; for the patients with ≤ 3 lesions with diameter ≥ 2 cm, a three-dimensional (3-D) conformal localised boost was given to increase the dosage to 56-60 Gy; and during radiotherapy, concurrent chemotherapy with topotecan was given (the chemoradiotherapy group, CRT). The patients with brain metastasis from lung cancer during the same period who received radiotherapy only were selected as the controls (the radiotherapy-alone group, RT).

RESULTS

From March 2009 to March 2012, both 38 patients were enrolled into two groups. The median progression-free survival(PFS) time , the 1- and 2-year PFS rates of CRT group and RT group were 6 months, 42.8%, 21.6% and 3 months, 11.6%, 8.7% (χ2 = 6.02, p = 0.014), respectively. The 1- and 2-year intracranial lesion control rates of CRT and RT were 75.9% , 65.2% and 41.6% , 31.2% (χ2 = 3.892, p = 0.049), respectively. The 1- and 2-year overall survival rates (OS) of CRT and RT were 50.8% , 37.9% and 40.4% , 16.5% (χ2 = 1.811, p = 0.178), respectively. The major side effects were myelosuppression and digestive toxicities, but no differences were observed between the two groups.

CONCLUSION

Compared with radiotherapy alone, whole-brain irradiation plus 3-D conformal boost irradiation and concurrent topotecan chemotherapy significantly improved the PFS rate and the intracranial lesion control rate of patients with brain metastases from lung cancer, and no significant increases in side effects were observed. Based on these results, this treatment method is recommended for phase III clinical trial.

Dose escalation of accelerated hypofractionated three-dimensional conformal radiotherapy (at 3 Gy/fraction) with concurrent vinorelbine and carboplatin chemotherapy in unresectable stage III non-small-cell lung cancer: a phase I trial

BACKGROUND

Accelerated hypofractionated radiotherapy can shorten total treatment time and overcome the accelerated repopulation of tumour cells during radiotherapy. This therapeutic approach has demonstrated good efficacy in the treatment of locally advanced non-small-cell lung cancer (NSCLC). However, the optimal fractionation scheme remains uncertain. The purpose of this phase I trial was to explore the maximum tolerated dose (MTD) of accelerated hypofractionated three-dimensional conformal radiotherapy (3-DCRT) (at 3 Gy/fraction) administered in combination with concurrent vinorelbine (NVB) and carboplatin (CBP) chemotherapy for unresectable stage III NSCLC.

METHODS

Previously untreated cases of unresectable stage III NSCLC received accelerated hypofractionated 3-DCRT, delivered at 3 Gy per fraction, once daily, with five fractions per week. The starting dose was 66 Gy and an increment of 3 Gy was utilized. Higher doses continued to be tested in patient groups until the emergence of dose-limiting toxicity (DLT). The MTD was regarded as the dose that was one step below the dose at which DLT occurred. Patients received at least one cycle of a concurrent two-drug chemotherapy regimen of NVB and CBP.

RESULTS

A total of 13 patients were enrolled and progressed through three dose escalation groups: 66 Gy, 69 Gy, and 72 Gy. No treatment-related deaths occurred. The major adverse events included radiation oesophagitis, radiation pneumonitis, and neutropenia. Nausea, fatigue, and anorexia were commonly observed, although the magnitude of these events was typically relatively minor. Among the entire group, four instances of DLT were observed, including two cases of grade 3 radiation oesophagitis, one case of grade 3 radiation pneumonitis, and one case of grade 4 neutropenia. All of these cases of DLT occurred in the 72 Gy group. Therefore, 72 Gy was designated as the DLT dose level, and the lower dose of 69 Gy was regarded as the MTD.

CONCLUSIONS

For unresectable stage III NSCLC 69 Gy (at 3 Gy/fraction) was the MTD of accelerated hypofractionated 3-DCRT administered in combination with concurrent NVB and CBP chemotherapy. The toxicity of this chemoradiotherapy regimen could be tolerated. A phase II trial is recommended to further evaluate the efficacy and safety of this regimen.

High-dose accelerated hypofractionated three-dimensional conformal radiotherapy (at 3 Gy/fraction) with concurrent vinorelbine and carboplatin chemotherapy in locally advanced non-small-cell lung cancer: a feasibility study

Background

Increasing the radiotherapy dose can result in improved local control for non-small-cell lung cancer (NSCLC) and can thereby improve survival. Accelerated hypofractionated radiotherapy can expose tumors to a high dose of radiation in a short period of time, but the optimal treatment regimen remains unclear. The purpose of this study was to evaluate the feasibility of utilizing high-dose accelerated hypofractionated three-dimensional conformal radiotherapy (at 3 Gy/fraction) with concurrent vinorelbine (NVB) and carboplatin (CBP) chemotherapy for the treatment of local advanced NSCLC.

Methods

Untreated patients with unresectable stage IIIA/IIIB NSCLC or patients with a recurrence of NSCLC received accelerated hypofractionated three-dimensional conformal radiotherapy. The total dose was greater than or equal to 60 Gy. The accelerated hypofractionated radiotherapy was conducted once daily at 3 Gy/fraction with 5 fractions per week, and the radiotherapy was completed in 5 weeks. In addition to radiotherapy, the patients also received at least 1 cycle of a concurrent two-drug chemotherapy regimen of NVB and CBP.

Results

A total of 26 patients (19 previously untreated cases and 7 cases of recurrent disease) received 60Gy-75Gy radiotherapy with concurrent chemotherapy. All of the patients underwent evaluations for toxicity and preliminary therapeutic efficacy. There were no treatment-related deaths within the entire patient group. The major acute adverse reactions were radiation esophagitis (88.5%) and radiation pneumonitis (42.3%). The percentages of grade III acute radiation esophagitis and grade III radiation pneumonitis were 15.4% and 7.7%, respectively. Hematological toxicities were common and did not significantly affect the implementation of chemoradiotherapy after supportive treatment. Two patients received high dose of 75 Gy had grade III late esophageal toxicity, and none had grade IV and above. Grade III and above late lung toxicity did not occur.

Conclusion

High-dose accelerated hypofractionated three-dimensional conformal radiotherapy with a dose of 60 Gy or greater with concurrent NVB and CBP chemotherapy might be feasible. However esophagus toxicity needs special attention. A phase I trial is recommended to obtain the maximum tolerated radiation dose of accelerated hypofractionated radiotherapy with concurrent chemotherapy.

Phase II trial of capecitabine combined with docetaxel in previously treated patients with non-small cell lung cancer: A randomized controlled study

Docetaxel alone has been confirmed to be beneficial to patients with advanced previously treated non-small cell lung cancer (NSCLC). However, the duration and survival time is short. The study of two-agent combination regimens has important clinical significance. We conducted this randomized controlled phase II trial to comparatively evaluate the efficacy and side effects of capecitabine combined with docetaxel in previously treated patients with NSCLC. Patients with previously treated NSCLC who failed first-line chemotherapy were randomized into two groups; one received capecitabine combined with docetaxel (XT group) and the other received docetaxel alone (T group). Patients in the XT group received chemotherapy as follows: capecitabine 625 mg/m(2), p.o. bid, days 5-18; and docetaxel 30 mg/m(2), days 1 and 8, while patients in the T group received docetaxel 35 mg/m(2) on days 1 and 8. The primary endpoint was time to progression (TTP), and secondary endpoints were overall survival (OS), response rate (RR) and disease control rate (DCR). Forty-eight patients were recruited (23 in the XT group and 25 in the T group). TTP, median survival time (MST) and 1-year OS rate in the XT group and the T group were 7 months, 12 months, 47.6% and 3 months, 12 months, 39.6%, respectively. The TTP in the XT group was significantly longer compared to that in the T group (χ(2)=4.763, p=0.029). The RR and DCR in the XT group and T group were 13.0% (3/23), 78.3% (18/23) and 12.0% (3/25), 76% (19/25), respectively. The difference was not significant (p>0.05). The major side effects observed in the two groups were neutropenia, fatigue and nausea, and toxicities were mild to modest. No severe cases of hand-foot syndrome were observed in the XT group. In conclusion, compared with docetaxel alone, capecitabine combined with docetaxel for patients with previously treated NSCLC achieved a significantly longer TTP and this regimen was well tolerated. The relatively high median TTP, 1-year OS rate and DCR encourage further evaluation of this regimen in a randomized phase III trial.

SDQR migrations in Caenorhabditis elegans are controlled by multiple guidance cues and changing responses to netrin UNC-6

The netrin guidance cue, UNC-6, and the netrin receptors, UNC-5 and UNC-40, guide SDQR cell and axon migrations in C. elegans. In wild-type larvae, SDQR migrations are away from ventral UNC-6-expressing cells, suggesting that UNC-6 repels SDQR. In unc-6 null larvae, SDQR migrations are towards the ventral midline, indicating a response to other guidance cues that directs the migrations ventrally. Although ectopic UNC-6 expression dorsal to the SDQR cell body would be predicted to cause ventral SDQR migrations in unc-6 null larvae, in fact, more migrations are directed dorsally, suggesting that SDQR is not always repelled from the dorsal source of UNC-6. UNC-5 is required for dorsal SDQR migrations, but not for the ventral migrations in unc-6 null larvae. UNC-40 appears to moderate both the response to UNC-6 and to the other cues. Our results show that SDQR responds to multiple guidance cues and they suggest that, besides UNC-6, other factors influence whether an UNC-6 responsive cell migrates toward or away from an UNC-6 source in vivo. We propose that multiple signals elicited by the guidance cues are integrated and interpreted by SDQR and that the response to UNC-6 can change depending on the combination of cues encountered during migration. These responses determine the final dorsoventral position of the SDQR cell and axon.

Netrin UNC-6 and the regulation of branching and extension of motoneuron axons from the ventral nerve cord of Caenorhabditis elegans

In the Caenorhabditis elegans embryo, some ventral midline motoneurons extend a process circumferentially to the dorsal midline and a process longitudinally along ventral nerve cord interneurons. Circumferential migrations are guided by netrin UNC-6, which repels motoneuron axons dorsally. Although the motoneuron cell bodies and the longitudinal axons are positioned along UNC-6-expressing interneurons in the ventral nerve cord, the circumferential processes extend only from the motoneuron cell bodies and from defined locations along some longitudinal axons. This implies a mechanism regulates motoneuron branching of UNC-6-responsive processes. We show that expression of unc-6DeltaC, which encodes UNC-6 without domain C, partially rescues circumferential migration defects in unc-6 null animals. This activity depends on the netrin receptors UNC-5 and UNC-40. These results indicate that UNC-6DeltaC can provide the circumferential guidance functions of UNC-6. Furthermore, we show that expression of unc-6DeltaC causes motoneuron branching and the extension of processes from abnormal positions along the ventral nerve cord. This activity is also UNC-5- and UNC-40-dependent. We propose that local interactions mediated by domain C regulate motoneuron branching and responsiveness to the UNC-6 cue.

Role of netrin UNC-6 in patterning the longitudinal nerves of Caenorhabditis elegans

The nervous system of Caenorhabditis elegans comprises circumferential and longitudinal axon tracts. Netrin UNC-6 is required for the guidance of circumferential axon migrations and is expressed by ventral neuroglia and neurons in temporally and spatially regulated patterns. Migrating axons mediate the UNC-6 signal through the UNC-5 and UNC-40 receptors. It is thought that UNC-6 is secreted and becomes associated with basement membranes and cell surfaces to form gradients that direct circumferentially migrating axons toward or away from the ventral UNC-6 sources. Little is known about the effects of UNC-6 on longitudinally migrating axons. In unc-6, unc-5, and unc-40 null mutants, some longitudinal nerves are dorsally or ventrally misdirected. Furthermore, the organization of axons are disrupted within nerves. We show that cells ectopically expressing UNC-6 can redirect the migrations of some neighboring longitudinal axons, suggesting that the gradients postulated to direct circumferential migration also help specify the dorsoventral positions of these longitudinal nerves. We also manipulated the temporal and spatial expression pattern of UNC-6 by two different means. First, we removed the PVT midline neuron which expresses UNC-6 for a short time during axon outgrowths. Second, we expressed UNC-6 uniformly in the nervous system throughout development. The results suggest that changing UNC-6 expression patterns modify the distribution of the cue by providing new localized sources. This new guidance information is critical for organizing the axons of longitudinal nerves.