MAPK11 (p38ß) is a major determinant of cellular radiosensitivity by controlling ionizing radiation-associated senescence: An in vitro study.

Background and purpose: MAPKs are among the most relevant signalling pathways involved in coordinating cell responses to different stimuli. This group includes p38MAPKs, constituted by 4 different proteins with a high sequence homology: MAPK14 (p38α), MAPK11 (p38ß), MAPK12 (p38γ) and MAPK13 (p38δ). Despite their high similarity, each member shows unique expression patterns and even exclusive functions. Thus, analysing protein-specific functions of MAPK members is necessary to unequivocally uncover the roles of this signalling pathway. Here, we investigate the possible role of MAPK11 in the cell response to ionizing radiation (IR). Materials and methods: We developed MAPK11/14 knockdown through shRNA and CRISPR interference gene perturbation approaches and analysed the downstream effects on cell responses to ionizing radiation in A549, HCT-116 and MCF-7 cancer cell lines. Specifically, we assessed IR toxicity by clonogenic assays; DNA damage response activity by immunocytochemistry; apoptosis and cell cycle by flow cytometry (Annexin V and propidium iodide, respectively); DNA repair by comet assay; and senescence induction by both X-Gal staining and gene expression of senescence-associated genes by RT-qPCR. Results: Our findings demonstrate a critical role of MAPK11 in the cellular response to IR by controlling the associated senescent phenotype, and without observable effects on DNA damage response, apoptosis, cell cycle or DNA damage repair. Conclusion: Our results highlight MAPK11 as a novel mediator of the cellular response to ionizing radiation through the control exerted onto IR-associated senescence.

p38ß (MAPK11) mediates gemcitabine-associated radiosensitivity in sarcoma experimental models.

BACKGROUND AND PURPOSE: Gemcitabine is an antitumour agent currently used in the treatment of several types of cancer with known properties as a radiosensitizer. p38MAPK signalling pathway has been shown to be a major determinant in the cellular response to gemcitabine in different experimental models. However, the molecular mechanism implicated in gemcitabine-associated radiosensitivity remains unknown. MATERIALS AND METHODS: The human sarcoma cell lines A673 and HT1080, and a mouse cell line derived from a 3-methylcholanthrene induced sarcoma were used as experimental models. Modulation of p38MAPKs was performed by pharmacological approaches (SB203580) and genetic interference using lentiviral vectors coding for specific shRNAs. Viability was assessed by MTT. Gene expression was evaluated by western blot and RT-qPCR. Induction of apoptosis was monitored by caspase 3/7 activity. Response to ionizing radiation was evaluated by clonogenic assays. RESULTS: Our data demonstrate that chemical inhibition of p38MAPK signalling pathway blocks gemcitabine radiosensitizing potential. Genetic interference of MAPK14 (p38α), the most abundantly expressed and best characterized p38MAPK, despite promoting resistance to gemcitabine, it does not affect its radiosensitizing potential. Interestingly, specific knockdown of MAPK11 (p38ß) induces a total loss of the radiosensitivity associated to gemcitabine, as well as a marked increase in the resistance to the drug. CONCLUSION: The present work identifies p38ß as a major determinant of the radiosensitizing potential of gemcitabine without implication of p38α, suggesting that p38ß status should be analysed in those cases in which gemcitabine is combined with ionizing radiation.

Efficacy and safety of ossein-hydroxyapatite complex versus calcium carbonate to prevent bone loss.

Objective: This study aimed to compare the efficacy and safety of ossein-hydroxyapatite complex (OHC) versus calcium carbonate (CC) for preventing bone loss during perimenopause in current clinical practice.Methods: The prospective, comparative, non-randomized, open-label study included 851 perimenopausal women with basal bone mineral density (BMD) T-score ≥-2 standard deviations (SDs). Participants received either OHC (712 mg calcium/day) or CC (1000 mg calcium/day) over 3 years. BMD was evaluated by dual-energy X-ray absorptiometry at the lumbar spine (L2-L4) at baseline and after 18 and 36 months of follow-up. Adverse drug reactions (ADRs) were also recorded.Results: In women receiving OHC, BMD at the L2-L4 site remained stable over the 3-year follow-up period (mean [SD] change 0.00 [0.11] g/cm2). BMD in the CC arm decreased -3.1% (mean [SD] - 0.03 [0.11] g/cm2). Between-group differences were statistically significant (p < 0.001) and favored OHC. ADRs were more frequent in the CC group (7.7% vs. 2.7% in the OHC group; p = 0.001), affecting primarily the gastrointestinal system.Conclusion: OHC showed greater efficacy and tolerability than CC for bone loss prevention in perimenopausal women in real-world practice. As the daily dose of calcium was higher in the CC group, the differences might be linked to the ossein compound in OHC.

P53 pathway is a major determinant in the radiosensitizing effect of Palbociclib: Implication in cancer therapy.

Targeting cell cycle has become one of the major challenges in cancer therapy, being Palbociclib, a CDK4/6 inhibitor, an excellent example. Recently, it has been reported that Palbociclib could be a novel radiosensitizer agent. In an attempt to clarify the molecular basis of this effect we have used cell lines from colorectal (HT29, HCT116) lung (A549, H1299) and breast cancer (MCF-7). Our results indicate that the presence of a p53 wild type is strictly required for Palbociclib to exert its radiosensitizing effect, independently of the inhibitory effect exerted on CDK4/6. In fact, abrogation of p53 in cells with functional p53 blocks the radiosensitizing effect of Palbociclib. Moreover, no radiosensitizing effect is observed in cells with non-functional p53, but restoration of p53 function promotes radiosensitivity associated to Palbociclib. Furthermore, the presence of Palbociclib blocks the transcriptional activity of p53 in an ATM-dependent-fashion after ionizing radiation exposure, as the blockage of p21/WAF1 expression demonstrates. These observations are a proof of concept for a more selective therapy, based on the combination of CDK4/6 inhibition and radiotherapy, which would only benefit to those patients with a functional p53 pathway.

Blockage of autophagic flux is associated with lymphocytosis and higher percentage of tumoral cells in chronic lymphocytic leukemia of B cells.

PURPOSE: Autophagy has lately emerged as an important biological process with implications in several hematological pathologies. Recently, a growing body of evidence supports a putative role of autophagy in chronic lymphocytic leukemia; however, no definitive clue has been established so far. To elucidate this issue, we have developed a pilot study to measure autophagic flux in peripheral blood mononuclear cells from chronic lymphocytic leukemia patients, and explored its correlation with classical clinical/analytical parameters. METHODS/PATIENTS: Thirty-three chronic lymphocytic leukemia patients participated in the study. Autophagic flux in peripheral blood mononuclear cells was determined by western blot measuring the levels of the proteins p62 and lipidated LC3. Moreover, p62 mRNA levels were analyzed by RT-qPCR. RESULTS: Lymphocytosis and the percentage of tumoral lymphocytes in chronic lymphocytic leukemia patients statistically correlate with a blocked autophagic flux. CONCLUSION: Alterations in autophagic flux could play an important role in the physiopathology of chronic lymphocytic leukemia.

Reduced salivary gland size and increased presence of epithelial progenitor cells in DLK1-deficient mice.

DLK1 (PREF1, pG2, or FA1) is a transmembrane and secreted protein containing epidermal growth factor-like repeats. Dlk1 expression is abundant in many tissues during embryonic and fetal development and is believed to play an important role in the regulation of tissue differentiation and fetal growth. After birth, Dlk1 expression is abolished in most tissues but is possibly reactivated to regulate stem cell activation and responses to injury. We have recently reported that DLK1 regulates many aspects of salivary gland organogenesis. Here, we have extended our studies of the salivary gland phenotype of Dlk1 knock-out mice. We have observed that salivary glands are smaller and weigh significantly less in both Dlk1 knock-out males and females compared with gender and age-matched wild-type mice and regardless of the natural sexual dimorphism in rodent salivary glands. This reduced size correlates with a reduced capacity of Dlk1-deficient mice to secrete saliva after stimulation with pilocarpine. However, histological and ultrastructural analyses of both adult and developing salivary gland tissues have revealed no defects in Dlk1 ((-/-)) mice, indicating that genetic compensation accounts for the relatively mild salivary phenotype in these animals. Finally, despite their lack of severe anomalies, we have found that salivary glands from Dlk1-deficient mice present a higher amount of CK14-positive epithelial progenitors at various developmental stages, suggesting a role for DLK1 in the regulation of salivary epithelial stem cell balance.

[Correspondence between the fatty acids in healthy children serum and in membrane phospholipids]. / Relación entre los ácidos grasos en suero y en los fosfolípidos de membrana en niños sanos.

INTRODUCTION: The diet is important in the supply of fatty acids in humans, especially those of the n-3 and n-6 families by its essentiality and related physiological function. It is important to have reference values in accessible biological samples: serum and erythrocyte membranes, in order to alleviate potential shortfalls. The objective is quantifying fatty acids present in these samples from C6 to C26. MATERIAL AND METHODS: the determinations of the fatty acids of 30 healthy children in serum and its corresponding membrane phospholipids from blood cells by lipid extraction, methylation, separation and quantification in gas chromatography with detection of masses have been. It is comparing the values obtained in each serum and its partner of cell membranes. RESULTS AND DISCUSSION: It is have obtained normal values in healthy children. The C16, which represent a quarter of all fatty acids, it is in the same proportion in both samples, in the rest of fatty acids, there is no clear correspondence between both values. In the n-6 family, the C18:2n6 is higher in serum against the C20:4n6 which is in the phospholipids. In the same way between the n-3 family, the C20:5n3 is higher in serum and the C22:6n3 is in membrane phospholipids. These values are cause of different processes, recent nutritional contribution to serum and with long-term implications and metabolic values in the phospholipids of membranes.

Introducción: La dieta es importante para el suministro de ácidos grasos del hombre, en especial los de las familias n-3 y n-6, por su esencialidad y las amplias funciones fisiológicas relacionadas. Es importante tener valores de referencia en las muestras biológicas accesibles, tales como suero y membranas eritrocitarias, con el fin de paliar posibles déficit. El objetivo del presente trabajo consiste en cuantificar los ácidos grasos esenciales (AGE) presentes en dichas muestras, desde la C6 hasta la C26. Material y métodos: Se han efectuado las determinaciones de los ácidos grasos de 30 niños sanos en suero y en sus correspondientes fosfolípidos de membrana de células sanguíneas, mediante su extracción lipídica, metilación, separación y cuantificación en cromatografía de gases con detección de masas. Se han comparado los valores obtenidos en cada suero y su pareja de membranas celulares. Resultados y discusión: Se han obtenido los valores normales en niños sanos. El C16, que supone la cuarta parte de todos los ácidos grasos, está en la misma proporción en ambas muestras; entre el resto, no se encuentra una correspondencia clara entre ambos valores. Entre los n-6, el C18:2n6 está en mayor proporción en suero, frente al C20:4n6 que lo está en los fosfolípidos. De igual forma, entre los n-3, el C20:5n3 está en mayor proporción en suero y el C22:6n3 lo está en fosfolípidos de membrana. Dichos valores son la causa de procesos distintos, aporte nutricional reciente para el suero y con implicaciones a largo plazo y metabólicas los valores en los fosfolípidos de las membranas.

[Trans fatty acids in the nutrition of children with neurological disorders]. / Ácidos grasos trans en la nutrición de niños con trastornos neurológicos.

INTRODUCTION: Trans-fatty acids are present in various foods, being the only source of the same in humans. Its presence in high concentrations is a risk factor for health, being involved in a series of events, cardiovascular, inflammatory, etc. Therefore, steps have been taken for its decrease in the diet. The aim is to determine serum and phospholipids of membranes in healthy children and neurological alterations. MATERIAL AND METHODS: It has analyzed the fatty acids trans in 34 healthy children and 374 with various neurological pathologies. Serum and blood cells, making the lipid extraction, samples have been separation of the phospholipids of cells membranes, methylation of fatty acids, separation by gas chromatography and quantification using mass detector. The data have been processed statistically. RESULTS: The distribution of trans fatty acids and their sum is not normally distributed, so its nonparemetric tests were used. The values are higher than in serum phospholipids and membrane with a weak but significant correlation. The tC18: 1 is in a double proportion in children with neurological disorders in healthy children, both in serum and membrane phospholipids, with significant differences. DISCUSSION: The highest proportion of trans-fatty acids in the group of children with neurological disorders is caused no doubt by an increase in intake, due to less adequate food.

Introducción: Los ácidos grasos trans (AGT) están presentes en diversos alimentos, y son la única fuente de los mismos en humanos. Su presencia en concentraciones elevadas supone un factor de riesgo para la salud, por lo que se ven implicados en toda una serie de eventos cardiovasculares, inflamatorios, etc. Por ello, se han adoptado medidas para su disminución en la dieta. Como objetivo, se pretende determinarlos en el suero y en los fosfolípidos de las membranas, tanto en los niños sanos, como en los que padecen alteraciones neurológicas. Material y métodos: Se han analizado los AGT de 34 niños sanos y de 374 con diversas patologías neurológicas. Se han utilizado muestras de suero y de células sanguíneas, para lo que se lleva a cabo una extracción lipídica, con separación de los fosfolípidos de las membranas de las células, metilación de los ácidos grasos, separación mediante cromatografía de gases y, finalmente, cuantificación mediante detector de masas. Los datos han sido procesados estadísticamente. Resultados: La distribución de los AGT y su suma no tienen una distribución normal, por lo que se han efectuado pruebas no paramétricas. Los valores son mayores en suero que en los fosfolípidos de membrana y con una correlación débil, aunque significativa. El tC18:1 tiene una proporción doble en los niños con trastornos neurológicos, frente a los niños sanos, tanto en el suero como en los fosfolípidos de membrana, con diferencias significativas. Discusión: La mayor proporción de AGT en el grupo de niños con trastornos neurológicos está causada, sin duda, por un incremento en su ingesta, lo que se debe a una alimentación menos adecuada.

[High ratio of omega 6/omega 3 ratio children with neuropathies; cause or effect]. / Índice elevado de ácidos grasos omega 6/omega3 en niños con neuropatía; causa o efecto.

INTRODUCTION: The n-3 and n-6 fatty acids compete for the same elongases and desaturases, still highly deficient synthesis of polyunsaturated fatty acids from n-3 linolenic acid. The n-3 polyunsaturated prevent disease and are important in the development and maintenance of neuronal activities, necessitating a proper relationship with their antagonists n-6. This paper studies the proportion of these fatty acids. MATERIAL AND METHODS: We analyzed the fatty acids of n- 3 and n-6 in sera and membrane phospholipid with 374 children neuropathies and 34 healthy children, using gas chromatography with mass detector. It has made the relevant statistical study. RESULTS: The n-3 (EPA and DHA) in serum and their corresponding membrane phospholipids correlate better than the n-6 family. The major n-6 (LA and ARA) are equally in serum, being significantly higher in phospholipids of healthy children. The n-3 (EPA and DHA) have higher values in healthy children, both in serum and phospholipids, their sum is equal to the membrane phospholipids. The n-6/n-3 ratio is higher in children with neurological disorder in both samples. CONCLUSION: Not being the cause of the high rate n-6/n- 3 neuropathy, however it is advisable to increase the intake of n-3, DHA particularly across the population, especially in children with neurological disorders.

Introducción: Los ácidos grasos n-3 y n-6 compiten por las mismas elongasas y desaturasas, siendo muy deficiente la síntesis de ácidos grasos poliinsaturados n-3 a partir de ácido linolénico. Los poliinsaturados n-3 previenen enfermedades y son importantes en el desarrollo y mantenimiento de las actividades neuronales, siendo necesaria una relación adecuada con sus antagonistas n- 6. En este trabajo se estudia la proporción de estos ácidos grasos. Material y métodos: Se han analizado los ácidos grasos n-3 y n-6 en sueros y fosfolípidos de membrana de 374 niños con neuropatías y de 34 niños sanos, mediante cromatografía de gases con detector de masas. Se ha realizado el estudio estadístico pertinente. Resultados: Los ácidos grasos n-3 (EPA y DHA) en suero y su correspondientes fosfolípidos de membrana correlacionan mejor que los de la familia n-6. Los mayoritarios n-6 (LA y ARA) están en igual proporción en sueros, siendo más elevados significativamente en los fosfolípidos de los niños sanos. Los n-3 (EPA y DHA) tienen valores más altos en los niños sanos, tanto en suero como en fosfolípidos, su suma se iguala en los fosfolípidos de membrana. El índice n-6/n-3 es mayor en los niños con trastorno neurológico en ambas muestras. Conclusión: No siendo la causa de la neuropatía el alto índice n-6/n-3, sin embargo es aconsejable incrementar la ingesta de n-3, sobre todo DHA en toda la población y en especial en los niños con trastornos neurológicos.

Role of the non-canonical notch ligand delta-like protein 1 in hormone-producing cells of the adult male mouse pituitary.

To better understand the role of the non-canonical Notch ligand delta-like protein 1 (DLK1), in hormone-producing cells, we studied the cell distribution and subcellular localisation of DLK1 in the pituitary of male adult 129/SvJ mice, and analysed the variations in the hormone-producing cells associated with the lack of this gene in Dlk1 knockout mice. The results obtained showed the presence of DLK1-immunoreactive (ir) cells in all hormone-producing cells of the anterior pituitary. Immunoelectron microscopy showed DLK1-ir in the rough endoplasmic reticulum and inside secretory vesicles, suggesting that DLK1 is released together with pituitary hormones. Moreover, we found that prolactin (PRL)-DLK1-ir cells are in intimate contact with follicle-stimulating hormone (FSH)-ir-DLK1-negative cells. In Dlk1 knockout mice, we detected a significantly lower number of gowth hormone (GH)-ir cells, a reduction in the FSH and PRL immunostaining intensity, and a significant decrease in FSH mRNA expression compared to wild-type mice. An increase in pituitary GH mRNA expression and serum leptin levels was also found. These findings provide evidence supporting several regulatory functions of DLK1 in the pituitary gland.

Consejo genético en el cáncer de mama y ovario. ¿Y luego qué? / Genetic counselling in breast and ovarian cancer. And then what?

El avance en la medicina preventiva y predictiva aborda el estudio genético con el fin de identificar la presencia de genes que se asocian a patologías como el cáncer de mama y ovario, y cuya prevención y diagnóstico precoz guardan una clara relación con la supervivencia. La identificación de estos genes supone, por una parte, poder establecer medidas de prevención, pero también puede ser origen de conflictos ante las decisiones o perspectivas que plantean los resultados. En la siguiente revisión planteamos la manera en que los médicos de atención primaria y ginecólogos pueden orientar a la mujer en esta situación (AU)

The advances in preventive and predictive medicine has led to carrying out genetic studies with the purpose of identifying the presence of genes that are linked to diseases, such as breast and ovarian cancer, where prevention and early diagnosis are clearly connected to their survival. The identification of these genes means, on the one hand, that prevention measures can be established, but it also can be the origin of conflicts as regards the decisions or the future prospects arising from the results. In this review, we explain how primary care doctors and gynaecologists can guide women in this situation (AU)

Isoflavones: effects on bone health.

BACKGROUND: There are many effects described, both experimental and clinical, that assess the relationship between isoflavones and bone. It has been hypothesized that isoflavones may have a positive effect on bone health. OBJECTIVE: To review the effects of isoflavones on biochemical markers of bone remodeling, bone density and bone quality, and finally on fracture incidence. METHODS: A systematic review was carried out of in vitro, animal, and human studies involving isoflavones and bone health. An electronic search was made, based on Internet search engines, MEDLINE (1966-June 2010) and the Cochrane Controlled Clinical Trials Register. This search was further supplemented by a hand-search of reference lists of selected review papers. RESULTS: After crossing-cleaning the reference lists, 737 studies dealing with isoflavones and bone were identified. Of these, 36 were considered selectable. From in vitro and animal studies, isoflavones appear to stimulate osteoblastic bone formation and inhibit osteoclastic bone resorption. Reviewed data show evidence of a beneficial effect of isoflavones on bone health in peri- and postmenopausal women when high-isoflavone soy protein is incorporated in the diet. Inconsistencies observed among data from different studies are related to differences in study design, the variety of soy sources of isoflavones, time of analysis, and the variability in the bioavailability and metabolism of isoflavones. CONCLUSIONS: Most of the studies suggested a positive relationship between isoflavones and bone health. Further well-controlled, randomized, double-blind, clinical trials with a larger sample population, longer duration, and examination of various dosages are needed to better elucidate the inter-relationship between isoflavones and bone loss and to clarify whether isoflavones could prevent bone fractures.

Effect of a compound containing isoflavones, primrose oil and vitamin E in two different doses on climacteric symptoms.

The object of this study was to evaluate the effect of different doses of a compound containing isoflavones 60 mg, primrose oil 440 mg and vitamin E 10 mg. (IOVE) on menopausal complaints. This was an open, multicentre, randomised, group comparative, efficacy and safety trial. A total of 1,080 postmenopausal women, with climacteric symptoms, were allocated into one of two treatment groups to receive one (Group 1; n = 562) or two IOVE capsules (Group 2; n = 518) per day. The Blatt - Kupperman scale and safety parameters including weight, body mass index, blood pressure and adverse effects were assessed at the first visit before initiating the treatment, and 3 - 6 months thereafter. In addition, cholesterol, high density lipoprotein (HDL), low-density lipoprotein (LDL) and triglyceride levels were measured at baseline and at the 6th month visit. Finally, at the end of follow-up, the patient's satisfaction was assessed. No differences between groups at the beginning of the study and during the follow-up were observed. A significant reduction in Blatt - Kupperman scores were observed in the two groups. In addition, the reduction of the symptoms was more intense in the first 3 months. Increasing doses of IOVE add no beneficial effects since both studied doses were equally effective in the reduction of climacteric complaints.

Sexualidad y calidad de vida en la mujer menopáusica / Sexuality and quality of life in the menopausal woman

La sexualidad es la forma de expresión de la intimidad, y en ella se manifiestan las dimensiones física, emocional, social y espiritual de la persona. Un primer paso para conseguir una sexualidad satisfactoria es disponer de una anticoncepción efectiva que libere el temor frente a un embarazo no deseado en una época donde las complicaciones maternas y perinatales están aumentadas. La sexualidad tiene una repercusión importante en la calidad de vida y aunque éste es un concepto subjetivo para cada individuo, resulta necesaria en la práctica clínica disponer de herramientas que permitan obtener una evaluación objetiva. Con esta idea se diseñó la escala Cervantes que permite la valoración de calidad de vida de la mujer posmenopáusiéa en nuestro medio y constatar los posibles cambios producidos tras una intervención terapéutica

The sexuality is the expression of the privacy, and relationship whit physical, emotional, social, and spiritual dimensions of the persono A first step to obtain a satisfactory sexuality is to have an effective contraception that it releases the fear a non wished pregnancy at a time where maternal and perinatal complications are increased. The sexuality has a important repercussion in the quality of life and although this it is a subjective concept for each individual, is necessary actually clinical to have tools that aIlow to obtain an objective evaluation. With this idea the Cervantes scale was designed that allows the valuation of quality of life of the menopausal woman in our country and to state the possible changes produced after a therapeutic intervention

Fitoestrógenos: introducción / No disponible

No disponible

El pie en el síndrome de Rubinstein-Taybi / The foot in Rubinstein-Taybi syndrome

El síndrome de Rubinstein-Taybi (SRT) es una enfermedad genética rara, multisistémica y de expresión clínica variable. Se caracteriza por retraso mental, primeros dedos de manos y pies anormalmente anchos y rasgos faciales característicos.Este síndrome es poco común y, aunque en ocasiones se hereda con carácter autosómico dominante, la mayoría de los casos se deben a una mutación genética durante el desarrollo fetal.Los afectados por este síndrome pueden presentar problemas en las extremidades inferiores; por ello, el conocimiento del síndrome puede ayudar a plantear alternativas de tratamiento eficaces.En este artículo se presenta el caso de una paciente de 14 años de edad con SRT con alteraciones en las extremidades inferiores, tales como luxación de la rodilla derecha, sindactilia completa y simple de segundo y tercer dedos del pie, pie cavo y marcha inestable. Se aborda el tema del tratamiento ortopédico aplicado a esta paciente (AU)

Specific regions of the extracellular domain of dlk, an EGF-like homeotic protein involved in differentiation, participate in intramolecular interactions.

The level of expression of dlk, an EGF-like protein possessing six EGF-like repeats in its extracellular region, is critical for 3T3-L1 fibroblasts to differentiate into adipocytes in response to IGF1. The mechanism of action of dlk is not well understood, but its localization on the cell membrane suggests that dlk may function as a receptor, as a ligand or as a regulatory protein modulating the binding, the signaling, or the expression of other molecules involved in cell differentiation and growth. In this work, we demonstrate, by using the Yeast Two-Hybrid system, that dlk interacts with itself through specific regions of its extracellular domain. The strongest interactions were observed between specific EGF-like repeats and between a non EFG-like region where unknown proteases act to generate soluble forms of dlk. These observations suggest that the interaction between two membrane dlk molecules belonging to the same or to different cells, or the interaction between soluble and membrane dlk variants, may be important to regulate dlk function.

Heterologous expression of the Phycomyces blakesleeanus phytoene dehydrogenase gene (carB) in Mucor circinelloides.

A phytoene dehydrogenase-deficient mutant of Mucor circinelloides accumulating only phytoene was transformed with the gene encoding the corresponding enzyme (carB gene) of Phycomyces blakesleeanus. Carotenoids derived from phytoene were detected in the transformants showing that the P. blakesleeanus carB gene complements the M. circinelloides carB mutation. These newly formed carotenoids accumulated in low quantities, indicating that functional complementation was poor. carB mRNA molecules correctly transcribed were detected in the transformants, but they represented a small proportion of the total population of carB-derived mRNAs, mostly constituted by truncated transcripts and by transcripts longer than the transcript that is functional in Phycomyces. These results showed that the P. blakesleeanus carB gene was expressed in M. circinelloides and suggested that the poor complementation observed was owing, at least in part, to the lack of specificity in the recognition of the transcription initiation and termination signals of the P. blakesleeanus carB gene by the M. circinelloides transcriptional machinery.