[Risk factors of occult lymph node metastasis of levels Ⅲ and Ⅳ in papillary thyroid carcinoma]

Objective: To investigate the potential risk factors for occult lateral cervical lymph node metastasis (LNM) to levels Ⅲ and Ⅳ in patients with papillary thyroid carcinoma (PTC) and the necessity of super-selective lateral lymph node dissection for patients harboring these metastases. Methods: This prospective study included PTC patients who were operated by the same surgeon in the Department of Head and Neck Surgery of Cancer Hospital, Chinese Academy of Medical Sciences from October 2015 through October 2019. Preoperative ultrasound and enhanced Computer Tomography (CT) did not denote suspected enlarged lymph nodes in the lateral neck. All patients underwent lymph node dissection in levels Ⅲ and Ⅳ on the basis of original thyroid collar incision after LNM to level Ⅵ was confirmed by preoperative fine needlebiopsy or intraoperative frozen pathology. Results: Of all 143 patients, 74 (51.7%) had occult LNM in levels Ⅲ and Ⅳ confirmed by postoperative pathology. The average number of metastasized lymph nodes in levels Ⅲ and Ⅳ was 2.64±1.80, and that in level Ⅵ was 3.77±3.27. There was a significant linear positive correlation between the number of metastasized lymph nodes in level Ⅵ and that in levels Ⅲ and Ⅳ (r=0.341, P<0.001). That the metastasized lymph nodes in level Ⅵ equals three was the best predictor of occult lateral LNM to levels Ⅲ and Ⅳ. Univariate analysis showed that age <55 years, tumor size ≥2.0 cm, number of metastasized lymph nodes in level Ⅵ ≥3, and percentage of metastasized lymph nodes in the total number of dissected lymph nodes in level Ⅵ >50% were associated with occult LNM in levels Ⅲ and Ⅳ (P<0.05). Multivariate analysis showed that number of metastasized lymph nodes in level Ⅵ≥3 was an independent risk factor for occult LNM in levels Ⅲ and Ⅳ (P=0.006). Conclusions: Age, tumor size and LNM in level Ⅵ were associated with occult lateral LNM in PTC patients. Lymph node dissection in levels Ⅲ and Ⅳ could be considered for selective patients, since it will help to avoid secondary operation for residual tumor or recurrence resulted from insufficient treatment without increasing the incidence of complications or affecting patients' appearances.

[Active surveillance for thyroid micro-malignant nodules]

Objective: To evaluate the effect of ultrasound diagnosis of thyroid micro-malignant nodules and accumulate practical experience for the management of active surveillance for them, so as to avoid overtreatment. Methods: A total of 949 patients who were diagnosed with thyroid malignant nodules using ultrasonography, with the nodules being less than 1 cm in size and without regional lymph node metastasis or distant metastasis, were included. They were treated by the same surgeon of the Department of Head and Neck Surgery, Cancer Hospital, Chinese Academy of Medical Sciences from February 2014 to December 2020. 112 patients chose immediate surgery. The rest patients were asked to accept ultrasound examination every 6 months to 1 year. Follow-up endpoints: tumor size growth of 3 mm, tumor volume increase greater than 50%, lymph node metastasis or distant metastasis. Results: The median follow-up time was 19 months. 713 patients underwent surveillance for more than 6 months. Of the 713 patients, 570 (79.9%) were women, with mean age at 43.5 years old. Tumor progression was observed in 47 (6.6%) patients with a cumulative incidence of 2.7% (1 year), 7.2% (2 years) and 9.5% (3 years). In multivariate analysis, patient age [HR=0.508, 95%CI: 0.275-0.939, P=0.031], lesion number [HR=2.945, 95%CI: 1.593-5.444, P=0.001] and tumor size [HR=2.245, 95%CI: 1.202-4.192, P=0.011] at the beginning of observation were independent risk factors for tumor progression in patients with minimal thyroid malignant nodules during follow-up. During a median (range) active surveillance of 19 (6-80) months, 74 patients chose surgery during the surveillance. Among the 186 patients who underwent surgery, only 3 patients were diagnosed with fibrotic nodules in pathology, while the rest were papillary thyroid carcinoma. The ultrasound accuracy reached 98.4%(183/186). Conclusions: Ultrasonography is an effective method of diagnosing malignant thyroid nodules. Thyroid micro-malignant nodules progress slowly. As a result, it is safe to observe them instead of taking immediate surgery. Patient age, lesion number and tumor size at the beginning of observation are independent risk factors for the tumor progression of malignant nodules.

[Prognostic value of the age-adjusted Charlson comorbidity index in patients over 60 years old with laryngeal squamous cell carcinoma]

Objective: To evaluate the value of the age-adjusted Charlson comorbidity Index (ACCI) in predicting the prognosis and guiding the clinical treatment of laryngeal squamous cell carcinoma (LSCC) in patients over 60 years old. Methods: Retrospective analysis of 249 cases of LSCC in Shanxi Provincial Cancer Hospital and First Hospital of Shanxi Medical University from 2008 to 2015 was performed. There were 234 males and 15 females, aged from 60 to 88 years. The clinical characteristics, treatment information and follow-up data were collected. ACCI was used to score the comorbidities of the patients. Receiver operating characteristic (ROC) curve was drawn and the patients were divided into high ACCI group and low ACCI group according to the cut-off value of ACCI. Prognostic factors were analyzed. Kaplan-Meier method was used for survival analysis, rank sum test was used for comparison between groups, χ² test was used for enumeration data. Results: Overall survival (OS) was 54.6%, progression-free survival (PFS) was 59.4%, and cancer-specific survival (CSS) was 58.6%. Both the median survival time and PFS time were 60 months. The best cutoff point of the ACCI group was 5. Cox multivariate analysis showed that ACCI was an independent risk factor for OS, PFS and CSS (OR=1.553, 1.499 and 1.534,respectively, all P<0.05). In the high ACCI group, OS (χ²=4.120 and 4.115,P<0.05) and CSS (χ²=4.510 and 5.009,P<0.05) of patients treated with surgery plus radiotherapy and patients with radiotherapy alone were better than those of patients with surgery alone (P<0.05). But in the low ACCI group, there was no significant difference in prognosis among the three treatment regimens (P>0.05). Conclusion: High ACCI offors important prognostic information for LSCC in patients over 60 years old, and can guide clinical treatment options.

[Preliminary study of superselective lymph node dissection in regional lateral cervical lymph node metastasis of papillary thyroid carcinoma]

Objective: To explore the applied value of super-selective cervical lymph node dissection in papillary thyroid carcinoma (PTC) patients with clinically suspicious lateral lymph node metastasis (LNM). Methods: We retrospectively analyzed the clinical data of 232 cN1b PTC patients who underwent surgery from September 2013 to May 2018 in the Department of Head and Neck Surgical Oncology, National Cancer Center. Among them, 90 cases received super-selective neck dissection (level Ⅲ and IV) and 142 cases underwent selective neck dissection (level Ⅱ-Ⅳ). The LNM of two groups were analyzed. Results: Postoperative pathological results showed that 173 cases had LNM in the central compartment. The LNM cases of level Ⅱ-Ⅳ were 47, 147 and 130, respectively. Eight patients of super-selective neck dissection and 6 of selective neck dissection had postoperative lymphatic fistulas (P=0.146). No patients in super-selective neck dissection group while 9 patients in the selective lymph node dissection group had postoperatively permanent impairment of shoulder mobility, the difference was statistically significant (P=0.015). In the super-selective neck dissection group, 2 patients had long-term postoperative incision discomfort, and 5 cases had obvious cicatrix after surgery. In the patients with selective neck dissection, 27 cases experienced long-term incision discomfort after surgery, and 26 patients had apparent scar tissue, the differences were statistically significant (P<0.005). There was no recurrence during the follow-up. Conclusions: Super-selective neck dissection is a feasible, safe and effective treatment for cN1b PTC patients. It can improve the quality of postoperative life and avoid the over treatment for patients.

[Comparison of quality of life of hypopharyngeal squamous cell carcinoma patients after laryngeal preservation surgery and total laryngectomy]

Objective: To evaluate and compare the quality of life (QOL) in patients with hypopharyngeal squamous cell carcinoma after laryngeal preservation surgery and total laryngectomy. Methods: We selected parts of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire C30 and the Head and Neck Module (EORTC QLQ-C30 and EORTC QLQ-H&N35) and designed the QOL questionnaire. We investigated 42 patients with hypopharyngeal squamous cell carcinoma underwent laryngeal preservation surgery and 38 patients underwent total laryngectomy by QOL questionnaire and followed up their survival. Results: The somatic function dimension, psychological function dimension, and social function dimension of patients underwent laryngeal preservation surgery were (92.46±15.71), (80.56±22.67) and (90.08±19.50), respectively, which were higher than (79.39±32.75), (68.42±25.05) and (61.84±29.55) of the total laryngectomy group (P<0.05), while the economic dimension was not significantly different between the two groups (P>0.05). The social function dimension (including social support and socialization, family relationship) of laryngeal preservation surgery group were (89.04±25.47) for postoperative time < 70 months and (90.94±13.28) for postoperative time ≥70 months, which were higher than (65.48±29.14) and (57.35±30.32) of the total laryngectomy group (P<0.01). Conclusions: The somatic function dimension, psychological function and social function of patients with hypopharyngeal squamous cell carcinoma underwent laryngeal preservation surgery obtain a better QOL than patients underwent total laryngectomy. Therefore, we should improve the laryngeal function and QOL of patients under the premise of ensuring the survival rate.

[The impact of surgical treatment on the life quality of patients with locally advanced hypopharyngeal carcinoma]

Objective: To explore the impact of surgical treatment on the life quality of patients with locally advanced hypopharyngeal carcinoma. Methods: A retrospective analysis of the clinical data of 21 patients with advanced hypopharyngeal carcinoma who underwent surgery at the Shenzhen Hospital of Chinese Academy of Medical Sciences Cancer Hospital from January 1, 2017 to December 31, 2019 was conducted. There were 3 patients with recurrence after radiotherapy and chemotherapy, 4 cases of postoperative recurrence, 3 cases of postoperative recurrence after radiotherapy and chemotherapy. Three cases were hypopharyngeal carcinoma with esophageal carcinoma and 8 cases were stage Ⅳ hypopharyngeal carcinoma. Among them, 3 cases were repaired by stomach, 4 cases by free jejunum, 2 case by great saphenous vein for internal carotid artery, 1 case by artificial blood vessel for internal carotid artery, 5 cases by transfer of pectoralis major musculocutaneous flap and 2 cases by transfer of submental island flap. The 21 patients were scored using the European Cancer Research and Treatment Organization's Quality of Life Head and Neck Tumor Special Scale (EORTC QLQ-H&N35) on the 3 months before and after surgery, and the changes in postoperative life quality were compared. Results: The preoperative life quality score of 21 patients was (56.86±7.95) points and life quality score of 3 months after operation was (50.93±7.91) points. The postoperative life quality was significantly improved (P<0.05). The improvement of the postoperative life quality of the patients mainly included the improvements of the head and neck pain, swallowing function, diet, taking analgesics and indwelling nasal feeding tubes. The preoperative scores were (7.58±1.56) points, (8.46±1.63) points, (7.94±0.43) points, (1.76±0.12) points and (1.86±0.28) points, respectively, while the scores of 3 months after operation were (5.02±1.23) points, (6.28±1.58) points, (6.34±0.36) points , (1.12±0.08) points and (1.24±0.18) points, the differences were statistically significant (all P<0.05). Conclusion: The flexible selection of flap repair for locally advanced hypopharyngeal carcinoma is still feasible, and surgery can improve the life quality of patients.

[Application of meticulous anatomy skills with straight bipolar electric coagulation forceps in thyroid surgery]

Objective: To compare the efficacies of the two techniques of "micro-hemostasis and micro-cutting" with straight bipolar electrocoagulation forceps and traditional clamp-ligation for hemostasia in thyroid surgery. Methods: A total of 228 patients who underwent surgical treatment for thyroid neoplasms in our hospital between January 2015 and December 2018 were retrospectively analyzed, including 50 males and 178 females, aged 23-68 years old. Of those, 150 cases as electric knife group received traditional thyroid surgery between January 2015 and December 2018 and 78 cases as bipolar electrocoagulation group received thyroid surgery by using the technique of bipolar electrocoagulation with meticulous anatomy between January 2018 and December 2018. The total operation time, single operation time, intraoperative hemorrhage, postoperative drainage volume on the first day, postoperative hoarseness and hypocalcemia were compared between the two groups. SPSS 16.0 was used to analyze the data. Results: The total operation time and intraoperative hemorrhage in the bipolar electrocoagulation group were significantly lower than those in the electric knife group ((59.33±18.29)min vs (77.21±25.39)min, (14.83±9.22)ml vs (36.86±11.80)ml, all P<0.01). The single operation time of the bipolar electrocoagulation group was shorter than that of the electric knife group((10.25±6.16) min vs (20.34±7.24)min, (16.25±7.15)min vs (35.68±8.25)min, (12.12±5.25)min vs (20.68±7.26)min, t value was 3.948,16.262,8.238, all P<0.01).There was no significant difference between the two groups in postoperative drainage volume on the first day (P>0.05) and the incidence of postoperative hoarseness (P>0.05), while the incidence of hypocalcemia in the bipolar electrocoagulation group(10.26%) was lower than that in the electric knife group(21.33%,χ(2)=4.353, P<0.05). Conclusions: The fine dissection for thyroid operation can be achieved by using straight bipolar electrocoagulation tweezers. The use of "micro-hemostasis" and "micro-cutting" technique with bipolar electrocoagulation tweezers can greatly reduce intraoperative bleeding, operation time and postoperative complication.

[Efficacy and safety of vandetanib on advanced medullary thyroid carcinoma: single center result from a phase Ⅲ study]

Objective: There is no effective therapy for patients with advanced medullary thyroid carcinoma (MTC). Vandetanib,a novel multitargeted receptor tyrosine kinase inhibitor, has previously shown antitumor activity in phase Ⅱ studies of patients with advanced MTC. This study was to evaluate the efficacy and the safety of vandetanib on advanced MTC. Methods: This study was an open, international multi-center phase Ⅲ clinical trial and the study number was NCT01298323. The single-center study was a sub-group analysis of the international study, which was conducted on 9 pathologically confirmed advanced MTC patients by Cancer Hospital Chinese Academy of Medical Sciences between March 2012 and October 2017. Vandetanib (300 mg) was orally administered daily till death or withdrawal. The efficacy was evaluated according to RECIST criteria and the adverse events were evaluated according to NCI criteria. Results: The objective response rate was 3/9,and the disease control rate was 4/9. The median progression-free survival was 44 months. All patients who had the elevated levels of calcitonin (CTN) and carcino-embryonic antigen (CEA) before treatment began to show the decreases in the level of CTN and CEA after 3 months and later showed again the increases in the levels of both tumor markers with tumor progression. By ROC curve analysis, CTN was of statistically significance(P<0.05, 95%CI 0.558-0.834), but CEA was not(P>0.05). Adverse events were generally mild (grade 1 or 2),including hypertension (9 cases),skin rash (9 cases), and diarrhea (6 cases). Two patients developed grade 3 elevation of serum glutamate pyruvate transaminase and one patient developed grade 3 elevation of drug-related bowel disease. No grade 4 drug-related adverse event occurred. Conclusions: Vandetanib is effective and well tolerated for patients with locally advanced or metastatic MTC who have no chance for surgery. This indicates the increase of CTN is clinically relevant to disease progression, but the number of patients are extremely low, and, therefore further research is needed. Long-term use of vandetanib may cause resistance.

[Primary research of early oral feeding after total laryngectomy]

Objective: To explore whether early oral feeding after total laryngectomy is safe and effective by evaluating the incidence of pharyngocutaneous fistula (PCF) and the hospital duration. Methods: A retrospective cohort study was conducted, including 52 patients underwent total laryngectomy, plus partial tongue base resection (n=2), partial pharyngectomy (n=1), or pedicle flap (n=2) between January 2012 and October 2017. Patients who had a history of preoperative radiotherapy, chemotherapy or chemoradiotherapy, previous surgery for larynx or pharynx and who had severe complications were excluded. Early oral feeding started between 48 h and 72 h postoperatively, while delayed oral feeding started within postoperative day 8-10. The incidences of PCF in two groups were compared to evaluate whether PCF and early oral feeding was related. Multi-variables analysis was conducted to evaluate risk factors for PCF. Results: PCF rate was 19.2% among all patients, 11.1% in patients with early oral feeding and 23.5% in patients with delayed oral feeding. No significant statistically difference in PCF rate was found between two groups (χ(2)=0.506, P=0.477). Multi-variables analysis showed that oral feeding time (early or delayed) was not a independent risk factor of PCF (Two classification response variable Logistic regression, P=0.200, OR=0.242, 95%CI[0.028-2.118]). But low preoperative albumin level was observed as an independent risk factor for PCF (P=0.039, OR=0.848, 95% CI [0.726-0.992]). A negative correlation was observed between preoperative albumin level and PCF. And also there was not a significant difference in hospital duration between patients with early oral feeding and delayed oral feeding(U=268, P=0.464). Conclusion: For patients total laryngectomy with no previous history of radiotherapy, chemotherapy, chemoradiotherapy, early oral feeding after surgery is safe and effective.

[Gastric pull-up reconstruction after pharyngoesphagectomy for advanced hypopharyngeal or cervical esophageal squamous cell carcinoma]

Objective: To analyze the clinical results of gastric pull-up reconstruction following total pharyngoesophagectomy. Methods: A total of 90 patients with hypopharyngeal or cervical esophageal cancinoma who underwent gatric pull-up reconstruction after pharyngoesophagectomy between June 2006 and June 2015 were reviewed retrospectively. Clinical data were analyzed. Rates of survival, recurrence and complicates were calculated with SPSS software. Results: Of 90 patients, 8 patients had hypopharyngeal cancinoma invading cervical esophagus, 51 patients had cervical esophageal carcinoma, and 31 patients had hypophageal and esophageal multiple parimary carcinomas. Forty patients were treated with surgery alone, 29 patients with planned surgery, and 21 patients with salvage surgery. After follow up of 6-104 months with a median of 22 months, 54 patients died and the total 3-year survival rate was 36.3%. Seventeen patients developed local recurrences and 10 patients cervical or mediastinal lymph node metastasis (LNM). The 3-year survival rates of patients with and without recurrence or LNM were respectively 5.9%, and 45.7% (χ²=11.564, P=0.001). Twenty-three patients developed distant metastasis. The 3-year survival rate of patients with and without distant metastasis were respectively 22.9% and 41.8% (χ²=4.534, P=0.033). Multivariate analysis showed local recurrence and distant metastasis as predictors for poor survival. The rates of perioperative mortality and anastomotic fistula were 3.3% (3/90) and 13.3%(12/90), respectively. Conclusions: Gastric pull-up reconstruction is a relatively safe and effective method for esophageal reconstruction after removal of hypopharyngeal or cervical esophageal carcinoma. Some patients could achieve good survival with low mortality and acceptable morbidity after multidisciplinary treatments.

Evolutionary constraints over microsatellite abundance in larger mammals as a potential mechanism against carcinogenic burden

Larger organisms tend to live longer, have more potentially carcinogenic cells, and undergo more cell divisions. While one might intuitively expect cancer incidence to scale with body size, this assertion does not hold over the range of different mammals. Explaining this lack of correlation, so-called 'Peto's paradox' can likely increase our understanding of how cancer defense mechanisms are shaped by natural selection. Here, we study the occurrence of microsatellite in mammal genomes and observe that animals with expanded body size restrain the number of microsatellite. To take into account of higher mutation rate in the microsatellite region compared to that of genome, limiting the abundance of somatic mutations might explain how larger organisms could overcome the burden of cancer. These observations may serve as the basis to better understand how evolution has modeled protective mechanisms against cancer development.

[Clinical analysis of lymphocytic thyroiditis coexistent with papillary thyroid carcinoma]

OBJECTIVE

To analyse the clinical features and treatment strategies of papillary thyroid carcinoma(PTC) coexistent with lymphocytic thyroiditis (LT).

METHODS

A total of 292 patients including 25 males and 267 females with LT and thyroid nodules treated in the department of head and neck surgery between Sep 2011 and Sep 2014 was analysed retrospectively and divided into two groups according to pathological results, of them 262 patients, with a median age of 47 years old, were LT with PTC and 30 patients, with a median age of 54 years old, were LT with benign nodules. Among 262 patients having LT with PTC, 259 were diagnosed as having malignant or suspicious malignant nodules and 3 having benign nodules with ultrasound before surgery, 98 cases were considered multifocal malignant nodules by preoperative ultrasound, and 112 cases were positive in cervical lymph nodes, including bilateral positive in 37 cases. Of 30 patients having LT with benign nodules, 14 were diagnosed malignant or suspicious malignant nodules and 16 benign nodules.

RESULTS

The mean age in 262 patients with PTC was less significantly than that in 30 patients with benign nodules (P<0.05). Ultrasound showed a high proportion of calcification and microcalcification in patients with PTC (34%) compared to patients with benign nodules(13%)(P<0.05). There were not significant differences in the mean levels of serum thyroid stimulating hormone(TSH) (2.80 vs 2.99 mU/L, P=0.233), thyroglobulin(TG) (27.14 vs 18.60 μg/L, P=0.747), and anti-thyroglobulin antibodies(ATG)(417.3 vs 378.7 U/ml, P=0.834) between patients with PTC and those with benign nodules. In patients with PTC, multifocal tumor accounted for 42%. The central and lateral lymph node metastasis rates were respectively 50% and 24%, and the occult metastasis rate of lateral neck lymph node was 16%. Univariate analysis showed that age less than 45 years old, multifocal tumor, tumor diameter more than or equal to 2cm and extrathyroidal extension were associated with central lymph node metastasis (P<0.05), but not with lateral neck metastasis. Multivariate analysis showed a closed correlation only between the lymph node metastases in central and lateral neck levels (P<0.05).

CONCLUSIONS

Calcification and microcalcification have the same importance in the ultrasonic diagnosis for PTC in patients with LT. Total thyroidectomy and prophylactic central lymph node should be a choice for LT with PTC. Lymph node metastasis in level Ⅵ indicates the possibility of lateral cervical lymph node metastasis in the patients having LT with PTC.

Cetaceans evolution: insights from the genome sequences of common minke whales

Background

Whales have captivated the human imagination for millennia. These incredible cetaceans are the only mammals that have adapted to life in the open oceans and have been a source of human food, fuel and tools around the globe. The transition from land to water has led to various aquatic specializations related to hairless skin and ability to regulate their body temperature in cold water.

Results

We present four common minke whale (Balaenoptera acutorostrata) genomes with depth of ×13 ~ ×17 coverage and perform resequencing technology without a reference sequence. Our results indicated the time to the most recent common ancestors of common minke whales to be about 2.3574 (95% HPD, 1.1521 – 3.9212) million years ago. Further, we found that genes associated with epilation and tooth-development showed signatures of positive selection, supporting the morphological uniqueness of whales.

Conclusions

This whole-genome sequencing offers a chance to better understand the evolutionary journey of one of the largest mammals on earth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1213-1) contains supplementary material, which is available to authorized users.

Comparison of genetic diversity between wild-caught broodstock and hatchery-produced offspring populations of the vulnerable Korean kelp grouper (Epinephelus bruneus) by microsatellites

The kelp grouper Epinephelus bruneus (Perciformes: Haemulidae), is one of the most economically important fishery resources in Korea. This fish is regarded as a target for prospective aquaculture diversification; therefore, maintenance of stock quality is important. To investigate the effects of current artificial reproduction in a hatchery facility, genetic variation in wild-caught broodstock and hatchery-produced offspring of kelp grouper was analyzed using eight polymorphic nuclear microsatellite DNA loci; 77 alleles were identified. Allelic variability ranged from 2 to 22 in the broodstock and from 1 to 10 in the offspring. The average observed and expected heterozygosities were 0.620 and 0.623 in the broodstock and 0.600 and 0.513 in the offspring, respectively. The possibility of a recent genetic bottleneck was suggested in both populations of E. bruneus. The minor, but significant, genetic differentiation (FST = 0.047, P < 0.05) observed was mainly due to statistically significant reductions in the number of alleles in the offspring compared with the broodstock, suggesting that these genetic changes could be related to genetic drift. Our results demonstrate the usefulness of microsatellite markers to monitor genetic variation and raise concerns about potential harmful genetic effects of inappropriate hatchery procedures. Therefore, genetic variation between broodstock and offspring in a hatchery should be monitored in both breeding and release programs as a routine hatchery operation, and inbreeding should ideally be controlled to improve kelp grouper hatchery management. Our data provide a useful genetic basis for future planning of sustainable culture and management of E. bruneus in fisheries.

Genetic differences between the wild and hatchery-produced populations of Korean short barbeled grunter (Hapalogenys nitens) determined with microsatellite markers

Short barbeled grunter, Hapalogenys nitens, is an economically important fishery resource. In Korea, this fish is in the early stage of domestication, and it has been regarded as the candidate marine fish species for prospective aquaculture diversification. This study presents a preliminary investigation of the future viability of sustainable fry production from short barbeled grunter. We used 12 polymorphic nuclear microsatellite DNA loci to analyze the possible genetic variability between the wild and hatchery-produced populations of short barbeled grunter from Korea and identified 91 alleles. Compared to the wild population, significant genetic changes including reduced genetic diversity (average allele number: 7.42 vs 3.75; average expected heterozygosity: 0.713 vs 0.598, Wilcoxon signed-rank test; P < 0.05) and differentiation [overall fixation index (FST) = 0.088, P < 0.01] occurred in the hatchery-produced population, as indicated by the observation of allele richness, unique allele, heterozygosity, FST, and results of molecular analysis of variance. These findings indicate that genetic drift may have promoted the differentiation between these 2 populations, which may have negative effects on sustainable fry production. Therefore, genetic variations of the wild and hatchery-produced populations should be monitored and subjected to control inbreeding through a commercial breeding program. The information presented by this paper would provide a useful genetic basis for future sustainable culturing planning and management of H. nitens.

New polymorphic microsatellite markers for the Korean manila clam (Ruditapes philippinarum) and their application to wild populations

Manila clam (Ruditapes philippinarum) is a valuable and intensively exploited shellfish species in Korea. Despite its importance, information on its genetic background is scarce. For the genetic characterization of R. philippinarum, expressed sequence tag-derived microsatellite markers were developed using next-generation sequencing. A total of 5879 tandem repeats containing di- to hexanucleotide repeat motifs were obtained from 236,746 reads (mean = 413 bp). Of the 62 loci screened, 24 (38.7%) were successfully amplified, and 10 were polymorphic in 144 individuals from 2 manila clam populations (Incheon and Geoje, Korea). The number of alleles ranged from 2 to 17 in the Incheon population and from 3 to 13 in the Geoje population (overall AR = 7.21). The mean observed and expected heterozygosities were estimated to be 0.402 and 0.555, respectively. Hence, there is less genetic variability in the Geoje population than in the Incheon population, although no significant reductions of genetic diversity were found between the populations (P > 0.05). However, significant genetic differentiation was detected between the populations (FST = 0.064, P < 0.001). Significant deviations from Hardy-Weinberg equilibrium and high inbreeding coefficients (mean FIS = 0.22-0.26) were detected in both populations. The 10 novel polymorphic microsatellite loci used in this study will be useful for future genetic mapping studies and for characterizing population structures, monitoring genetic diversity for successful aquaculture management, and developing conservation strategies for manila clam populations in Korea.

Characterization of novel microsatellite markers derived from Korean rose bitterling (Rhodeus uyekii) genomic library

Korean rose bitterling (Rhodeus uyekii) is a freshwater fish endemic to Korea. Natural populations of this species have experienced severe declines as a result of habitat fragmentation and water pollution. To conserve and restore R. uyekii, the genetic diversity of this species needs to be assessed at the population level. Eighteen novel polymorphic microsatellite loci for R. uyekii were developed using an enriched partial genomic library. Polymorphisms at these loci were studied in 150 individuals collected from three populations. The number of alleles at each locus ranged from 3 to 47 (mean = 17.1). Within the populations, the observed heterozygosity ranged from 0.032 to 1.000, expected heterozygosity from 0.082 to 0.967, and polymorphism information content from 0.078 to 0.950. Six loci showed significant deviation from Hardy-Weinberg equilibrium after Bonferroni's correction, and no significant linkage disequilibrium was detected between most locus pairs, except in three cases. These highly informative microsatellite markers should be useful for genetic population structure analyses of R. uyekii.

Genetic characterization of hatchery populations of Korean spotted sea bass (Lateolabrax maculatus) using multiplex polymerase chain reaction assays

The spotted sea bass, Lateolabrax maculatus, is an important commercial and recreational fishery resource in Korea. Aquacultural production of this species has increased because of recent resource declines, growing consumption, and ongoing government-operated stock release programs. Therefore, the genetic characterization of hatchery populations is necessary to maintain the genetic diversity of this species and to develop more effective aquaculture practices. In this study, the genetic diversity and structure of three cultured populations in Korea were assessed using multiplex assays with 12 highly polymorphic microsatellite loci; 144 alleles were identified. The number of alleles per locus ranged from 6 to 28, with an average of 13.1. The mean observed and expected heterozygosities were 0.724 and 0.753, respectively. Low levels of inbreeding were detected according to the inbreeding coefficient (mean FIS = 0.003-0.073). All hatchery populations were significantly differentiated from each other (overall fixation index (FST) = 0.027, P < 0.01), and no population formed a separate cluster. Pairwise multilocus FST tests, estimates of genetic distance, mantel test, and principal component analyses did not show a consistent relationship between geographic and genetic distances. These results could reflect the exchange of breeds and eggs between hatcheries and/or genetic drift due to intensive breeding practices. For optimal resource management, the genetic variation of hatchery stocks should be monitored and inbreeding controlled within the spotted sea bass stocks that are being released every year. This genetic information will be useful for the management of both L. maculatus fisheries and the aquaculture industry.

Mitochondrial and microsatellite DNA analyses showed comparative genetic diversity between parent and offspring populations of Korean black rockfish in a hatchery facility

The black rockfish, Sebastes inermis (Sebastidae), is an important commercial fishery resource in Korea. As a preliminary investigation into the effect of artificial reproduction in a hatchery facility, the genetic divergence between parent and offspring populations of black rockfish was accessed using 10 polymorphic nuclear microsatellite DNA loci and a mitochondrial (mt) control gene. All loci that were screened showed marked polymorphisms. mtDNA control region sequences were also highly variable. Of approximately 350 base pairs (bp) sequenced, 52 variable sites, comprising 56 base substitutions, were found among 233 individuals. Offspring populations showed less genetic variability than the parent population in terms of numbers of microsatellite alleles and mtDNA haplotypes, as well as mtDNA haplotype diversity. Statistical analysis of the fixation index (ΦST and F(ST)) and analysis of molecular variance using both DNA markers showed significant genetic differences between the parent and offspring populations. These results suggest that random genetic drift and/or inbreeding events, as well as artificial selection and founder effects, occurred when the offspring strain was reproduced in a hatchery facility despite thousands of males and females from different hatcheries being maintained for artificial reproduction. Therefore, it is necessary to improve current hatchery programs by monitoring genetic variation in both the broodstock and progeny and controlling inbreeding within stocks in commercial breeding facilities to maintain the production of high-quality black rockfish. This information will be useful for determining suitable guidelines for establishing and maintaining cultured stocks and the aquaculture industry of S. inermis.

Genetic relationships of Pacific abalone (Haliotidae) species determined using universal rice primer-polymerase chain reaction fingerprinting

Random amplified polymorphic DNA (RAPD) with universal rice primers (URP) was used to identify species and to determine phylogenetic relationships for the 6 economically important Korean Pacific abalone species: Haliotis discus hannai, H. discus discus, H. madaka, H. gigantea, H. diversicolor supertexta, and H. diversicolor diversicolor, whose morphological differentiation is difficult. Of the 12 URPs used in this study, 7 were effective in producing reproducible RAPD markers for these 6 species. Amplifications with the 7 URP primers yielded 129 reproducible amplified fragments ranging between 100 and 6000 bp in length. The dendrogram generated by the unweighted pair-group method using arithmetic averages showed that the 6 species were divided into 4 groups at 0.44 similarity level, indicating that they were genetically distant from each other and had little internal phylogenetic resolution. One group included H. discus hannai, H. discus discus, H. madaka, and H. gigantea, which were divided into 2 groups at 0.52 similarity level: one group of H. discus hannai, H. discus discus, and H. madaka, and the other of H. gigantea. H. diversicolor supertexta and H. diversicolor diversicolor belonged to the other group. Furthermore, the reproducible pattern of amplified DNA bands by URP primers indicated the possibility of using these as molecular markers for the discrimination of the 6 Pacific abalone species. These results suggest that the URP-PCR approach will be a useful tool for obtaining accurate taxonomic identification and genetic relationship of Korean Pacific abalones, which is one of the first prerequisites in effective conservation programs.

Comparative genetic variability between broodstock and offspring populations of Korean starry flounder used for stock enhancement in a hatchery by using microsatellite DNA analyses

Korean starry flounder, Platichthys stellatus (Pleuronectidae), is one of the most economically important fishery resources in Korea. We investigated the effect of current artificial reproduction in a hatchery facility, genetic divergence between the broodstock and their offspring populations of starry flounder in a hatchery strain to be stocked into natural sea areas was accessed using 9 polymorphic nuclear microsatellite DNA loci. High levels of polymorphism were observed between the 2 populations. A total of 96 alleles were detected at the loci, with some alleles being unique in the broodstock. Allelic variability ranged from 8 to 17 in the broodstock and from 7 to 12 in the offspring population. Average observed and expected heterozygosities were estimated at 0.565 and 0.741 in the broodstock samples and 0.629 and 0.698 in the offspring population, respectively. Although no statistically significant reductions were found in heterozygosity or allelic diversity in the offspring population, a considerable loss of rare alleles was observed in the offspring population compared with that in the broodstock. Significant genetic difference was detected between the broodstock and offspring populations (FST = 0.021, P < 0.05). These results suggest that more intensive breeding practices for stock enhancement might have resulted in a further decrease of genetic diversity. Thus, genetic variations of broodstock and progeny should ideally be monitored in both breeding and release programs as a routine hatchery operation in order to improve the starry flounder hatchery management. This information might be useful for fishery management and aquaculture industry of P. stellatus.

Genetic characterization of Mytilus coruscus and M. galloprovincialis using microsatellite markers

Korean (hard-shelled) mussels (Mytilus coruscus) are an economically important endemic marine bivalve mollusk of Korea; yet, the population has rapidly declined because of overharvesting and habitat competition from the invasive Mytilus galloprovincialis species. The population structures of M. coruscus and M. galloprovincialis were analyzed by next-generation sequencing using 5 microsatellite markers specifically developed for M. coruscus. M. galloprovincialis had an average of 5.4 alleles per locus (range = 2-10), with an average allelic richness of 4.9 per locus (range = 2.0-9.3). M. coruscus had an average of 5.7 alleles per locus (range = 2-13), with an average allelic richness of 5.2 per locus (range = 2.0-11.9). Excessive homozygosity was observed at 3 loci, which was assumed to be due to the presence of null alleles at these loci. Pairwise multilocus FST estimates showed that the M. coruscus and M. galloprovincialis populations were clearly separated. Six populations of M. galloprovincialis from the western, eastern, and southern coast of Korea formed 2 separate clusters, indicating that more than 2 populations of M. galloprovincialis have been introduced to the Korean Peninsula. Hybrids between M. coruscus and M. galloprovincialis were not identified, probably because of genetic differences or different habitat preferences. Further genetic information is required to perform selective breeding, population management, and restoration of M. coruscus.

Population genetic structure of wild and hatchery black rockfish Sebastes inermis in Korea, assessed using cross-species microsatellite markers

The population structure of the black rockfish, Sebastes inermis (Sebastidae), was estimated using 10 microsatellite loci developed for S. schlegeli on samples of 174 individuals collected from three wild and three hatchery populations in Korea. Reduced genetic variation was detected in hatchery strains [overall number of alleles (N(A)) = 8.07; allelic richness (A(R)) = 7.37; observed heterozygosity (H(O)) = 0.641] compared with the wild samples (overall N(A) = 8.43; A(R) = 7.83; H(O) = 0.670), but the difference was not significant. Genetic differentiation among the populations was significant (overall F(ST) = 0.0237, P < 0.05). Pairwise F(ST) tests, neighbor-joining tree, and principal component analyses showed significant genetic heterogeneity among the hatchery strains and between wild and hatchery strains, but not among the wild populations, indicating high levels of gene flow along the southern coast of Korea, even though the black rockfish is a benthic, non-migratory marine species. Genetic differentiation among the hatchery strains could reflect genetic drift due to intensive breeding practices. Thus, in the interests of optimal resource management, genetic variation should be monitored and inbreeding controlled within stocks in commercial breeding programs. Information on genetic population structure based on cross-species microsatellite markers can aid in the proper management of S. inermis populations.

Genetic differentiation among populations and color variants of sea cucumbers (Stichopus japonicus) from Korea and China

The Far Eastern sea cucumber, Stichopus japonicus, is a favored food in Eastern Asia, including Korea, Japan, and China. Aquaculture production of this species has increased because of recent declines in natural stocks and government-operated stock release programs are ongoing. Therefore, the analyses of genetic structure in wild and hatchery populations are necessary to maintain the genetic diversity of this valuable marine resource. In addition, given that sea cucumber color affects market price, with the rare, possibly reproductively isolated, red type being the most valuable, an understanding of the genetic structure and diversity in color variation of green and red types is necessary. We analyzed the genetic structure of wild and hatchery-produced green type S. japonicus from Korea and China, and wild red type from Korea using 9 microsatellite makers. The number of alleles per locus ranged from 11 to 29 across all populations. The mean allele numbers of the green types from Korea (10.6) and China (10.1) were similar, but differed slightly from that of the red type (9.1). Pairwise multilocus F(ST) and genetic distance estimations showed no significant differences between the green types from Korea and China, whereas the differences between the green and red types were significant. This was clearly illustrated by a UPGMA dendrogram, in which the two close subclusters of green types were completely separated from the red type. In addition, the allele frequencies of the green and red types were significantly different. Assignment tests correctly assigned 100% (quality index 99.97%) of individuals to their original color types and demonstrated the feasibility of microsatellite analysis for discrimination between color types.