Draft genome sequence of Streptomyces coelicoflavus ZG0656 reveals the putative biosynthetic gene cluster of acarviostatin family α-amylase inhibitors

AIMS

The aims of this study are to obtain the draft genome sequence of Streptomyces coelicoflavus ZG0656, which produces novel acarviostatin family α-amylase inhibitors, and then to reveal the putative acarviostatin-related gene cluster and the biosynthetic pathway.

METHODS AND RESULTS

The draft genome sequence of S. coelicoflavus ZG0656 was generated using a shotgun approach employing a combination of 454 and Solexa sequencing technologies. Genome analysis revealed a putative gene cluster for acarviostatin biosynthesis, termed sct-cluster. The cluster contains 13 acarviostatin synthetic genes, six transporter genes, four starch degrading or transglycosylation enzyme genes and two regulator genes. On the basis of bioinformatic analysis, we proposed a putative biosynthetic pathway of acarviostatins. The intracellular steps produce a structural core, acarviostatin I00-7-P, and the extracellular assemblies lead to diverse acarviostatin end products.

CONCLUSIONS

The draft genome sequence of S. coelicoflavus ZG0656 revealed the putative biosynthetic gene cluster of acarviostatins and a putative pathway of acarviostatin production.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, S. coelicoflavus ZG0656 is the first strain in this species for which a genome sequence has been reported. The analysis of sct-cluster provided important insights into the biosynthesis of acarviostatins. This work will be a platform for producing novel variants and yield improvement.

SU-E-T-596: Choroidal Metastases Irradiation with Volumetric Modulated Arc Radiotherapy

PURPOSE

Intraocular metastases are present in up to 10% of patients with systemic malignancies. With tumor cells spreading hematogenously, the posterior choroid is frequently involved because of its rich vasculature. We treated a woman who developed bilateral choroidal metastases from breast cancer. For the patient, we designed three radiotherapy techniques. The study was to find the dosimetric differences between them.

METHODS

For the patient with bilateral choroidal metastases, three-dimensional conformal radiotherapy (3D-CRT), inverse intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (V-MAT) plans were designed. The prescription dose was 60 Gy in 30 fractions. The dose distribution in the target, the dose to the organs at risk, total MU and delivery time were compared.

RESULTS

In 3D-CRT, IMRT and V-MAT plans, the volume of target in 100% prescription dose were 92.5%, 93.3% and 92.0% respectively. V-MAT plan showed the best conformity and homogeneity in target. IMRT plan showed a better homogeneity than 3D-CRT plan. In 3D- CRT, IMRT and V-MAT plans, the max doses on left lens were 975.3 cGy, 739.9cGy, 870.2 cGy respectively. The max doses on right lens were 929.9 cGy, 802.9 cGy and 889.0 cGy respectively. V-MAT plan showed the lowest value for the max dose on left optic nerve and the lower value for the right one compared to 3D-CRT plan. The MUs were 386, 973, 709 and the delivery times were 10 min, 14min and 1.6 min respectively in 3D-CRT, IMRT and V-MAT. V-MAT could significantly reduce the delivery time.

CONCLUSIONS

V-MAT plan showed the best conformity and homogeneity in target. IMRT showed the lowest value in the max doses to lenses though the delivery time was longest. Overall, V-MAT showed a similar or better dose distribution, and most importantly, improved treatment delivery efficiency. With the results, V-MAT technology could be expected to choroidal metastases.

Nanovector delivery of siRNA for cancer therapy

RNA interference holds the promise to knock down expression of every cancer gene. Both academic laboratories and pharmaceutical companies have committed heavily on manpower and financial resources to develop small interfering RNA (siRNA) cancer therapeutics over the last decade. Although significant advances have been made in the design of siRNA therapeutics and mechanism of action on cancer cell killing, there are still many hurdles to overcome including effective delivery of therapeutics in vivo. Nanotechnology has had an important role in the development of delivery vectors so far. This article summarizes current nanovectors for siRNA delivery, discusses technical challenges in overcoming biological barriers, and introduces the multistage vector system for tumor-specific delivery.

Two splice variants of the bovine lactoferrin gene identified in Staphylococcus aureus isolated from mastitis in dairy cattle

Bovine lactoferrin (bLF) is a member of the transferrin family; it plays an important role in the innate immune response. We identified novel splice variants of the bLF gene in mastitis-infected and healthy cows. Reverse transcription-polymerase chain reaction (RT-PCR) and clone sequencing analysis were used to screen the splice variants of the bLF gene in the mammary gland, spleen and liver tissues. One main transcript corresponding to the bLF reference sequence was found in three tissues in both healthy and mastitis-infected cows. Quantitative real-time PCR analysis showed that the expression levels of the LF gene's main transcript were not significantly different in tissues from healthy versus mastitis-infected cows. However, the new splice variant, LF-AS2, which has the exon-skipping alternative splicing pattern, was only identified in mammary glands infected with Staphylococcus aureus. Sequencing analysis showed that the new splice variant was 251 bp in length, including exon 1, part of exon 2, part of exon 16, and exon 17. We conclude that bLF may play a role in resistance to mastitis through alternative splicing mechanisms.

Thermolabile antifreeze protein produced in Escherichia coli for structural analysis

The only hyperactive antifreeze protein (AFP) found to date in fishes is an extreme variant of the 3-kDa, alpha-helical, alanine-rich type I AFP, which is referred to here as type Ih. Purification of the 33-kDa homodimeric AFP Ih from a natural source was hampered by its low levels in fish plasma; by the need to remove the more abundant smaller isoforms; and by its extreme thermolability. Moreover, ice affinity as a purification tool was spoiled by the tendency of fish IgM antibodies to bind to ice in the presence of AFPs. In order to produce enough protein for crystallography we expressed AFP Ih as a recombinant protein in the Arctic Express® strain of Escherichia coli at 12 °C, just below the thermal denaturation temperature of 16-18 °C. His-tags were not useful because they compromised the activity and yield of AFP Ih. But in the absence of fish antibodies we were able to recover 10-mg quantities of the antifreeze protein using two cycles of ice affinity purification followed by anion-exchange chromatography to remove contaminating chaperones. The purified recombinant AFP Ih yielded diffraction-quality crystals with an extremely asymmetrical unit cell. By transferring the genes of the chaperones into a methionine auxotroph we were able to grow this host at low temperatures and produce sufficient selenomethionine-labeled AFP Ih for crystallography.

ADP-Mg2+ bound to the ATP-grasp domain of ATP-citrate lyase

Human ATP-citrate lyase (EC 2.3.3.8) is the cytoplasmic enzyme that catalyzes the production of acetyl-CoA from citrate, CoA and ATP. The amino-terminal portion of the enzyme, containing residues 1-817, was crystallized in the presence of tartrate, ATP and magnesium ions. The crystals diffracted to 2.3 Å resolution. The structure shows ADP-Mg(2+) bound to the domain that possesses the ATP-grasp fold. The structure demonstrates that this crystal form could be used to investigate the structures of complexes with inhibitors of ATP-citrate lyase that bind at either the citrate- or ATP-binding site.

Papillary carcinoma in a thyroglossal duct remnant. Three case reports and discussion on management

OBJECTIVE

To report three cases of papillary thyroglossal duct carcinoma (TDCa), and to discuss the diagnostic and therapeutic methods.

CASE REPORTS

We studied the clinical, pathological findings of the tumor, treatment and outcome data on 3 patients treated at our Institution for a papillary TDCa carcinoma and we compared the results with the published cases. Preoperative Fine Needle Aspiration (FNA) and intraoperative frozen section exam was performed in patients 1 and 2. Following the Sistrunk operation (SO), limited thyroidectomy were performed on patients 1 and 2, due to benign lesion. Neck dissections were performed on patients 2 and 3 (second operation after initial SO in other Institute), due to regional lymphadenopathy. The diagnosis of papillary TDCa was confirmed in all cases. Lymph nodes metastases were identified in patients 2 and 3. All patients were treated with levothyroxine therapy. After a median follow-up of 59 months, all patients are alive without recurrence.

CONCLUSIONS

Papillary TDCa is a rare malignancy with excellent prognosis. FNA and intraoperative frozen section exam are the most useful methods for confirmatory diagnosis. Resection of the thyroglossal duct carcinoma by the Sistrunk operation is an adequate surgical approach. Further thyroidectomy should be limited to one either lobe or pyramidal lobe in high risk patients. Total thyroidectomy is recommended only when there is clinical evidence of multifocal malignancy in thyroid gland. Postoperative hormone suppression is advocated.

[Research progress of biological characteristics and advantages of Wharton's jelly-mesenchymal stem cells]

OBJECTIVE

To summarize the research progress of biological characteristics and advantages of Wharton's jelly-mesenchymal stem cells (WJ-MSCs).

METHODS

The related literature on the biological characteristics of WJ-MSCs, umbilical cord blood MSCs (UBMSCs) and bone marrow MSCs (BMSCs) was extensively reviewed and analyzed.

RESULTS

A large number of MSCs which are able to self-replicate, self-renew and have high proliferation and multipotent differentiation can be isolated from the Wharton's jelly of umbilical cord. WJ-MSCs have many advantages in isolation time, isolation efficiency, expansion time, passage capacity, expansion capacity when compared with UBMSCs and BMSCs.

CONCLUSION

WJ-MSCs have numerous advantages of convenient and abundant sources, relatively pure, non-ethical issues, and so on, which can be used for cell transplant therapy, gene therapy, and the ideal seed cells of building tissue engineered organ, so they provide new ideas for tissue regeneration repair and reconstruction.