Combining fermentation to produce O-succinyl-l-homoserine and enzyme catalysis for the synthesis of l-methionine in one pot.

The biosynthetic pathway of l-methionine in microorganisms was complex and regulated at multiple levels. In this study, a two-step method for l-methionine production combined fermentation and biocatalysis was realized in one pot. The O-succinyl-l-homoserine (OSH) producing strain Escherichia coli W3110(DE3) ΔIJB∗TrcmetL/pTrc-metAfbr-Trc-thrAfbr-yjeH (ΔIJB) was constructed initially. OSH in the fermentation supernatant was then converted to l-methionine in the presence of O-succinyl-l-homoserine sulfhydrylase (OSHS) and sodium methanethiol. The titer of l-methionine could reach 21.1 g/L after 88 h (84 h fermentation and 4 h catalysis) in a two-step method (process 1). In a one-pot two-strain system (process 2), two strains ΔIJB and E. coli BL21(DE3)/pET28b-OSHS-cutinase were co-cultured, and 8.24 g/L l-methionine was obtained. In another one-pot one-strain system (process 3), strain E. coli ΔIJB/pET28b-OSHS-cutinase could co-express OSHS and cutinase during ΔIJB fermentation at the same time, obtaining 13.6 g/L l-methionine in a 5 L fermentor after 84 h. By comparing the three processes for l-methionine production based on the process 1, the simplified process in process 3 provided in this study showed potent in the large-scale production of l-methionine with convenient handling and production efficiency, but further works still need to be carried out to improve the l-methionine production.

Identification and Characterization of an O-Succinyl-L-Homoserine Sulfhydrylase From Thioalkalivibrio sulfidiphilus.

L-methionine is an important natural amino acid with broad application prospects. A novel gene encoding the enzyme with the ability to catalyze O-succinyl-L-homoserine (OSH) to L-methionine was screened and characterized. The recombinant O-succinyl-L-homoserine sulfhydrylase from Thioalkalivibrio sulfidiphilus (tsOSHS) exhibited maximum activity at 35°C and pH 6.5. OSHS displayed an excellent thermostability with a half-life of 21.72 h at 30°C. Furthermore, the activity of OSHS increased 115% after Fe2+ added. L-methionine was obtained with a total yield reaching 42.63 g/L under the concentration of O-succinyl-L-homoserine 400 mM (87.6 g/L). These results indicated that OSHS is a potential candidate for applying in the large-scale bioproduction of L-methionine.

O-Succinyl-l-homoserine overproduction with enhancement of the precursor succinyl-CoA supply by engineered Escherichia coli.

O-Succinyl-l-homoserine (OSH) is an important platform chemical in production of C4 chemicals such as succinic acid, homoserine lactone, γ­butyrolactone, and 1,4­butanediol. The production of OSH through chemical method or the current engineering strain is difficult and not optimal, and thereby there remains a need to develop new engineering strategy. Here, we engineered an OSH overproducing Escherichia coli strain through deleting the degradation and competitive pathways, overexpressing thrA and metL to enhance the metabolic flux from l-asparate to l-homoserine. Additionally, increasing the precursor succinyl-CoA supply through simultaneously knocking out sucD and overexpressing sucA further increased the yield of OSH. The engineered strain OSH9/pTrc-metA11-yjeH with above strategies produced OSH at the concentration of 24.1 g/L (0.609 g/g glucose) in batch fermentation. To gain detailed insight into metabolism of the engineered strain, comparative metabolic profiling was performed between the engineered and wide-type strain. The metabolomics data deciphered that the carbon was directed toward the OSH biosynthesis resulting in less flexibility of the genetically modified strain than the wide-type strain.

The distribution of melanocytes and the degradation of melanosomes in fetal hair follicles.

There have been many studies about the formation, storage, transport and degradation of melanosomes in epidermal melanocytes but studies of melanocytes and melanosomes in fetal hair follicles (HFs) have been limited and ambiguous. The goal of this study was to investigate the distribution of melanocytes and the degradation of melanosomes in fetal HFs. After obtaining approval and informed consent for the study, a scalp specimen from a 5 month gestational age fetus was obtained and was divided into two parts. One part was subjected to immunohistochemical staining with the melanocyte-specific marker HMB-45 and was then observed by light microscopy to detect the distribution of melanocytes in HFs. The other part underwent conventional processing for transmission electron microcopy (TEM). Subsequently, the morphology of melanosomes in HF melanocytes and their degradation in cortical keratinocytes were observed. Immunohistochemically, scattered round melanocytes lacking dendrites were mainly observed along the outer root sheath of the lower part of the HF. A few fusiform or tri-dendritic melanocytes were located at the bottom of the hair bulbs. Significantly melanized melanocytes with multiple dendrites were concentrated in the pigmented area in the center of the hair bulbs, only above the dermal papilla. Analysis by TEM revealed melanocytes containing melanosomes at all stages of development. Autophagosomes containing stage mature IV melanosomes were observed in some melanocytes. Many phagolysosomes containing numerous melanosomes were observed in the cortical keratinocytes. Some phagolysosomes were concentrically surrounded by 3-5 layers of endoplasmic reticulum. Melanosomes that had been degraded or were being degraded in phagolysosomes in keratinocytes had lost their integrity and had become an ill-defined melanosomal dust that were arranged irregularly. Partial melanin particles were released into the cytosol. Melanocytes in different regions of fetal HFs had different morphologies and were at various stages of differentiation. Fetal HF melanocytes contained not only melanosomes at different developmental stages, but autophagosomes were seen occasionally. Melanosomes were degraded into irregular pigment particles in the phagolysosomes of cortical keratinocytes. These results provide important clues to elucidate the mechanism of melanosome biodegradation.

Crossed Total Hemiatrophy Associated with Atrophoderma of Pasini-Pierini.

A 45-year-old Chinese man had begun to show asymmetry of the face 30 years previously. Subsequently, he developed visual extinction of the right eye, slight numbness, and weakness of the left extremities. Simultaneously, multiple atrophic brownish patches occurred on his side. He denied prior trauma or tick bites at those sites. There was no report of preceding redness, induration, or a history of trauma. The atrophic lesions extended and enlarged slowly. Ten years previously, some brownish patches with normal texture had appeared on the right side of the trunk. There was no further progression of the lesions. In November 2010, the patient consulted our department for the final diagnosis and prognosis of his disease. He did not suffer from epileptic seizures and had no history of a tick bite or Lyme disease.

rhCSF3 accelerates the proliferation of human melanocytes in culture through binding CSF3R and the expression of CSF3R transcripts.

Melanogenic paracrine and autocrine cytokine networks have recently been discovered in vitro between melanocytes and other types of skin cells. Granulocyte colony-stimulating factor receptor (CSF3R) controls the survival, proliferation and differentiation of many kinds of cells, including neutrophils. To understand the function of CSF3R and recombinant human granulocyte colony-stimulating factor (rhCSF3) on melanocyte proliferation, this study compared the expression of CSF3R and the effects of rhCSF3 in primary human melanocytes, neutrophils and HEL 92.1.7 cells. The results show that CSF3R is localized in the cytoplasm and on cell membranes of melanocytes and neutrophils. The percentage of CSF3R(+) melanocytes was higher than CSF3R(+) HEL 92.1.7 cells, but was lower than CSF3R(+) neutrophils. Both CSF3R mRNA and CSF3R protein levels in melanocytes were higher than in HEL 92.1.7 cells, but were lower than in neutrophils. Treatment with rhCSF3 increased the proliferation of human melanocytes, but not their tyrosinase activity. Transcripts of CSF3R in human melanocytes, M14, A375 melanoma and A431 squamous cell carcinoma cells were also detected. Expression of the CSF3R V3 transcript was lower in melanocytes than in M14, A375 melanoma and A431 squamous cell carcinoma cells. In conclusion, rhCSF3 can promote melanocyte proliferation through CSF3R without affecting tyrosinase activity.

Spectrum of dermoscopic patterns in lichen planus: a case series from China.

BACKGROUND: Dermoscopy has been shown to be a promising method to facilitate the diagnosis of lichen planus (LP) outside of China. OBJECTIVE: To investigate the spectrum of dermoscopic patterns in Chinese LP patients. METHODS: The clinical data and dermoscopic patterns of nine LP cases with a total of 43 lesions were evaluated. RESULTS: To the naked eye, 20.97% of the lesions exhibited graying Wickham striae (WS); however, 37.5% presented with white streaks of annular, reticular, or leaf venation patterns under dermoscopy. Blue-white veils were occasionally observed in the center. Pigment patterns varied from dots, globules, and peppered pigment to pigmented lines, which were unrelated to the pigment network of the skin. At the periphery of the WS, red fine lines ran parallel to the delicate white streaming lines. CONCLUSIONS: WS exhibits five morphological patterns (leaf venation, reticular, white dots, circular and radial streaming) and three color patterns (homogeneous crystalline white, blue-white veil and yellowish-white). The pigment patterns consisted of dots/globules, peppered pigments and pigment. streaming lines.

Centrally located acquired bilateral nevus of ota-like macules: a bizarre pattern.

A 22-year-old woman was referred to our hospital for pigmented lesions located on her face. These had gradually increased during the past 4 years. Computed tomography (CT) of her head revealed no significant parenchymal abnormalities of temporal, maxillary and sphenoid bones or of either parietal bone. Further screening, including neurologic, ophthalmologic, orthopedic, and visceral investigations, did not reveal any abnormalities. There was no family history of abnormal cutaneous pigmentation.

Three paraneoplastic signs in the same patient with gastric adenocarcinoma.

This is the report of a 76-year-old male with typical lesions of acanthosis nigricans maligna (ANM), florid cutaneous papillomatosis (FCP), and tripe palms (TP) for 2 years. He did not have any gastrointestinal complaints. Pathologic findings of skin supported the diagnosis of ANM. Because gastric adenocarcinoma is the most common neoplasm associated with these paraneoplastic dermatoses, further tests were carried out. Endoscopic examination was performed and an adenocarcinoma of the esophagogastric junction was confirmed. Meanwhile, multiple small polyps in the middle and the lower thirds of the esophagus were observed. The patient was referred for further evaluation and subsequent surgical resection of the tumor.Acanthosis nigricans (AN) is a hyperkeratotic mucocutaneous eruption of heterogenous etiology, which is characterized by hyperpigmentation, velvety cutaneous thickening, intensified skin markings, and development of verrucous excrescences typically involving the intertriginous areas. AN is classified into benign and malignant forms on the basis of clinical associations. Malignant acanthosis nigricans (MAN) tends to be extensive and involves mucosal surfaces, mostly in elderly people. Florid cutaneous papillomatosis (FCP), also known as the Schwartz-Burgess syndrome, is characterized by the rapid appearance of multiple verrucous lesions that are clinically indistinguishable from common warts [1]. Tripe palms (TP) is characterized by diffuse, yellowish palmar hyperkeratosis, with enhancement of the epidermal ridges on the hands (dermatoglyphics), resembling intestinal villosities [1]. The association of these three paraneoplastic dermatoses (FCP, ANM and TP) in the same patient has been reported. Herein, we report an elderly male with three paraneoplastic dermatoses for two years. On the initial presentation, he did not report any systemic complaints; diagnostic tests confirmed the presence of a gastric adenocarcinoma.

Culture of amelanotic melanocytes derived from human fetal hair follicles.

Human melanocyte stem cells (MSCs) or melanoblasts are not well-investigated owing to the devoid of suitable culture system. Establishing cell lines of MSCs and/or their progenies from human hair follicles will provide a better opportunity to satisfy clinical needs and to enable a deeper understanding of hair-related diseases. In the present study, we cultured melanocytes derived from human fetal hair follicles, perform immunocytochemistry and Fontana Masson staining on them, and employed atomic force microscopy (AFM) and scanning electron microscopy to observe their subtle morphologies. The results show that the cultured melanocytes have a bipolar or tripolar appearance, which obviously differ from cultured epidermal melanocytes. Compared to cells derived from adult human hair follicles, these cells display a high proliferative capability and exhibit a clonal growth behavior. At the second passage, all these cells were positive for immunocytochemical staining with the NKI/beteb monoclonal antibody and Fontana Masson staining. Under AFM, the cells exhibited rounded, oval, triangular, or quadrangular perikarya, from which two or three dendrites arose. The dendritic arbor was not homogeneous but appeared as spindle-shaped dendritic swellings, knob-like processes, without any filopodia arising from the dendrites or the cell body. Without using a feeder layer, we successfully obtained the clonal growth of melanocytes from human fetal HFs, suggesting that the medium was suitable for the growth of MSCs and their progenies.

Stem cell factor combined with matrix proteins regulates the attachment and migration of melanocyte precursors of human hair follicles in vitro.

In conjunction with matrix proteins, stem cell factor (SCF) plays an important role in the migration of melanocyte precursors (MPs) derived from the mouse embryo. However, no studies have demonstrated an effect of SCF on human follicular MPs migration in vitro. In this report, first we demonstrate the immature state of the follicular MPs. Then cell attachment rate was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Standard 48-well chemotaxis chambers were used for a transfilter migration assay. F-actin was labeled by rhodamine-conjugated phalloidin, and then organization of the actin cytoskeleton was observed by confocal microscope. In the results, we directly show that MPs adhere more strongly to fibronectin (FN), laminin (LN) and type IV collagen (CIV) than to the negative control. SCF decreased the adhesion of MPs to FN and CIV. A chemotaxis analysis showed that FN and CIV have chemotactic effects on MPs. FN showed an obvious increase in chemotactic effects on MPs with SCF treatment comparing with the control group, but there were no significant changes in the levels of chemotaxis with CIV and LN when the cells were treated with SCF. SCF was chemotactic to MPs, and the presence of FN caused a statistically significant increase in MPs migration at various concentrations of SCF. Furthermore, we showed that SCF, in combination with FN, could induce an apparent increase in actin stress fiber formation in MPs. Our results indicate that SCF, in combination with matrix proteins and in particular with FN, regulates the movement of MPs by both altering cell attachment and increasing cell chemotaxis.

Pentachrome vitiligo in a segmental pattern.

We describe a 22-year-old male with a pigmentary disorder that first appeared when he was 5 years of age. Examination revealed that these lesions were distributed in a segmental pattern on the left side of his trunk. Five shades of colors--white, tan, medium brown, dark brown, and black--were present. The patient told us there had been no preceding inflammation in the affected areas. A biopsy specimen from the inguinal region showed a complete absence of melanocytes, whereas most of the hyperpigmented areas were characterized by increased amounts of epidermal pigment and numbers of melanocytes. Based on the clinical appearance, pentachrome vitiligo in a segmental type was diagnosed.

Familial progressive hypo- and hyperpigmentation: a variant case.

Familial progressive hyper- and hypopigmentation (FPHH) is characterized by diffuse hyperpigmentation with variable intensity. Cafe'-au-lait macules and larger hypopigmented ash-leaf macules are also present. Herein, we reported a variant case of FPHH. The patient was a two-year-old Chinese girl showing diffuse hyper- and hypopigmented lesions, longitudinal melanonychia in both thumbs, and infantile seizures, without any lentigines.

Bilateral milia en plaque in a 6-year-old Chinese boy.

Milia en plaque is a rare variant of miliathat occurs spontaneously on an erythematous base without identifiable causative factors. Approximately 40 cases have been recorded in the literature. Most occurred in the periauricular area, affected middle-aged patients, and showed a predilection for women. Here, we report a case of milia en plaque on the bilateral posterior helices in a 6-year-old Chinese boy.