Melanocortin‐1 receptor structure and functional regulation

The melanogenic actions of the melanocortins are mediated by the melanocortin‐1 receptor (MC1R). MC1R is a member of the G‐protein‐coupled receptors (GPCR) superfamily expressed in cutaneous and hair follicle melanocytes. Activation of MC1R by adrenocorticotrophin or α‐melanocyte stimulating hormone is positively coupled to the cAMP signaling pathway and leads to a stimulation of melanogenesis and a switch from the synthesis of pheomelanins to the production of eumelanic pigments. The functional behavior of the MC1R agrees with emerging concepts in GPCR signaling including dimerization, coupling to more than one signaling pathway and a high agonist‐independent constitutive activity accounting for inverse agonism phenomena. In addition, MC1R displays unique properties such as an unusually high number of natural variants often associated with clearly visible phenotypes and the occurrence of endogenous peptide antagonists. Therefore MC1R is an ideal model to study GPCR function. Here we review our current knowledge of MC1R structure and function, with emphasis on information gathered from the analysis of natural variants. We also discuss recent data on the regulation of MC1R function by paracrine and endocrine factors and by external stimuli such as ultraviolet light.     

The production of different morphs by alate viviparae of the aphid Myzus persicae temporarily exposed to long scotophases

The development of alatae of the green peach aphid, Myzus persicae, as gynoparae rather than as virginoparae was investigated with regard to the number of exposures to a long-night (LN) regime of 15 h darkness per diem which the aphids experienced before and/or after their birth. The minimum number of exposures to LN that resulted in all of the alatae developing into gynoparae was two prenatal plus one postnatal or one prenatal plus two postnatal, provided the scotophases in these treatments were at least 12 h long. A cumulative effect of several successive exposures to LN was also evident when the presumptive alatae were exposed to LN either from birth or not until several days after birth. Fewer exposures to LN were needed in the former case.

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Zusammenfassung Die Entwicklung von Alatae der grünen Pfirsichblattlaus, Myzus persicae, hauptsächlich zu Gynoparae, eher als zu Virginoparae, wurde im Hinblick auf den Einfluss der Anzahl an Langnächten (LN: 15 Studen Dunkelheit pro Tag), denen die Aphiden vor und/oder nach der Geburt ausgesetzt waren, untersucht. Zur ausschliesslichen Entwicklung aller Alatae zu Gynoparae waren mindestens 2 prenatale und eine postnatale LN-Exposition oder eine prenatale und 2 postnatale LN-Expositionen notwendig, vorausgesetzt die Dunkelphasen betrugen mindestens 12 Stunden. Ausserdem zeigte sich ein kumulativer Effect durch mehrere, aufeinanderfolgende LN-Expositionen, wenn die Alatae diesen von Geburt an, oder einige Tage nach der Geburt, ausgesetzt waren. Im ersten Fall waren weniger LN-Expositionen notwendig.

     

Protein polymorphism in a feral population of the pigeon Columba livia domestica

Sixteen enzymatic and non-enzymatic proteins of the pigeon Columba livia domestica were examined electrophoretically. These proteins were presumed to be under control by 22 loci. Of the 22 loci, 6 were defined as polymorphic and 15 as monomorphic. Another locus was variable, but the variation was not genetically interpretable. Average heterozygosity calculated over 21 loci was 0.075.     

A new lipoprotein allotype Lprs and allele Lpr1,3 in the pig

Specific alloprecipitins were found in blood plasma of pigs, immunized by sera of Lpr1 positive donors. These precipitins detected a new allotype of the lipoprotein Lpr system which was designated Lpr3. Genetic studies confirmed its codominant inheritance and subgroup character. This linear subgroup of allotype Lprl is controlled by the allele Lpr^1,3. Investigations in populations of 14 pig breeds showed significant interbreed differences in the frequencies of alleles Lpr¹, Lpr² and Lpr^1,3.     

Prenatal diagnosis of Pallister-Killian syndrome and literature review

Pallister-Killian syndrome (PKS) is a rare sporadic genetic disorder usually caused by mosaicism of an extra isochromosome of 12p (i(12p)). This retrospective study analysed the prenatal ultrasound manifestations and molecular and cytogenetic results of five PKS foetuses. Samples of amniotic fluid and/or cord blood, skin biopsy and placenta were collected. Conventional karyotyping and single nucleotide polymorphism array (SNP array) were performed on all the amniotic fluid or cord blood samples. Copy number variants sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were also used for the validation for one foetus. All the five foetuses were from pregnancies with advanced parental age. Two foetuses involved structural abnormalities and one foetus had only soft markers, all of which included increased nuchal translucency. The rest two foetuses had normal ultrasounds in the second trimester, which has rarely been reported before. The karyotype revealed typical i(12p) in four cases and a small supernumerary marker chromosome consisting of 12p and 20p in the remaining one case. The proportion of cells with i(12p) ranged from 0 to 100% in cultural cells, while SNP array results suggested 2−4 copies of 12p. For one foetus, metaphase FISH showed normal results, but the interphase FISH suggested cell lines with two, three and four copies of 12p in the amniotic fluid. Advanced parental age may be an important risk factor for PKS, and there were no typical ultrasound manifestations related to PKS. A combination of karyotype analysis and molecular diagnosis is an effective method for the diagnosis of PKS.     

Angiotensin converting enzyme gene polymorphism studies: A case-control study

Mild gestational hyperglycemia (MGH) is a very common complication of pregnancy that is characterized by intolerance to glucose. The association of angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism to MGH has been previously reported. In this study, we evaluated the association between ACE polymorphism and the risk of MGH in a Saudi population. We conducted a case-control study in a population of 100 MGH patients and 100 control subjects. ACE gene polymorphism was analyzed by the novel approach of tetraprimer amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR). The frequency of ACE polymorphism was not associated with either alleles or genotypes in MGH patients. Glucose concentration was found to be significantly associated with the MGH group. Our study suggests that ACE genotypes were not associated with ACE polymorphism in a Saudi population.     

Expression patterns and association analysis of the porcine DHX58 gene

RIG-1 signalling is responsible for the detection of cytoplasmic viral RNA molecules. DEXH (Asp-Glu-X-His) box polypeptide 58 (encoded by DHX58) is a negative regulator of the RIG-1 signalling pathway. In human, the DHX58 gene can be upregulated and can inhibit the RIG-1 signalling pathway during viral infection. In this study, porcine DHX58 gene expression patterns were studied. According to our results, the porcine DHX58 gene was upregulated not only by the stimulation of Poly I:C but also by the stimulation of 1ipopolysaccharides (LPS). One polymorphism (g.4919G>C), detected in the ninth intron, was significantly associated with some blood parameters including the red cell distribution width of 1-day-old pigs and white blood cell counts, lymphocyte absolute counts, and platelet distribution width of 17-day-old pigs (P < 0.05). Moreover, the individuals with the genotype GG have a significantly higher mean white blood cell count than individuals with genotype CC or GC (P < 0.05). Our study indicates that DHX58 is an important gene that is associated with the immune response in swine.     

Polymorphism of the SLB serologically defined (non-MHC) alloantigenic system in pigs

Six new antigenic specificities (designated SLB-2 to SLB-7) detectable with polyclonal reagents in the complement-dependent lymphocytotoxic test were determined in the SLB alloantigenic system of pigs. The SLB specificities (including the previously described SLB-1) are controlled by 13 alleles. An analysis of a further 121 double backcross matings (with 817 offspring) confirmed that the products of SLB alleles segregated independently of the SLA haplotypes (swine MHC). In addition, in 112 families of the same mating type (with 746 progeny) the map distance of the SLB locus and the highly polymorphic L blood group locus was found to be 7.82 centimorgans in the heterogametic sex and 12.57 centimorgans in the homogametic sex.     

Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies

Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre‐ or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism.