Subfunctionalization of arylalkylamine N‐acetyltransferases in the sea bass Dicentrarchus labrax: two‐ones for one two

Melatonin is an important component of the vertebrates circadian system, synthetized from serotonin by the successive action of the arylalkylamine N‐acetyltransferase (Aanat: serotonin→N‐acetylserotonin) and acetylserotonin‐O‐methyltransferase (Asmt: N‐acetylserotonin→melatonin). Aanat is responsible for the daily rhythm in melatonin production. Teleost fish are unique because they express two Aanat genes, aanat1 and aanat2, mainly expressed in the retina and pineal gland, respectively. In silico analysis indicated that the teleost‐specific whole‐genome duplication generated Aanat1 duplicates (aanat1a and aanat1b); some fish express both of them, while others express either one of the isoforms. Here, we bring the first information on the structure, function, and distribution of Aanat1a and Aanat1b in a teleost, the sea bass Dicentrarchus labrax. Aanat1a and Aanat1b displayed a wide and distinct distribution in the nervous system and peripheral tissues, while Aanat2 appeared as a pineal enzyme. Co‐expression of Aanats with asmt was found in the pineal gland and the three retinal nuclear layers. Enzyme kinetics indicated subtle differences in the affinity and catalytic efficiency of Aanat1a and Aanat1b for indolethylamines and phenylethylamines, respectively. Our data are consistent with the idea that Aanat2 is a pineal enzyme involved in melatonin production, while Aanat1 enzymes have a broader range of functions including melatonin synthesis in the retina, and catabolism of serotonin and dopamine in the retina and other tissues. The data are discussed in light of the recently uncovered roles of N‐acetylserotonin and N‐acetyldopamine as antioxidants, neuroprotectants, and modulators of cell proliferation and enzyme activities.     

The mitochondrial fluorescent dye rhodamine 123 is a high‐affinity substrate for organic cation transporters (OCTs) 1 and 2

Rhodamine 123 is a fluorescent cationic dye commonly used as a mitochondrial probe and known or suspected to be transported by certain drug membrane transporters. The present study was designed to characterize the putative interactions of rhodamine 123 with human organic cation transporter (OCT) 1 and OCT2. Intracellular uptake of the dye was demonstrated to be enhanced in both hOCT1‐ and hOCT2‐overexpressing HEK293 cells when compared with control HEK293 cells. This increase of rhodamine 123 influxes was found to be a saturable carrier‐mediated process, with low K_m values (K_m = 0.54 μm and K_m = 0.61 μm for transport of the dye in hOCT1‐ and hOCT2‐positive HEK293 cells, respectively). Known inhibitors of hOCT1 and hOCT2 activities such as verapamil, amitriptyline, prazosin, and quinine were next demonstrated to decrease rhodamine 123 accumulation in hOCT1‐ and hOCT2‐overexpressing HEK293 cells. In addition, the dye was found to inhibit hOCT1‐ and hOCT2‐mediated uptake of tetraethylammonium (TEA), a model substrate for both hOCT1 and hOCT2; rhodamine 123 appeared nevertheless to be a more potent inhibitor of hOCT1‐mediated TEA transport (IC₅₀ = 0.37 μm ) than of that mediated by hOCT2 (IC₅₀ = 61.5 μm ). Taken together, these data demonstrate that rhodamine 123 is a high‐affinity substrate for both hOCT1 and hOCT2. This dye may be therefore useful for fluorimetrically investigating cellular hOCT1 or hOCT2 activity, knowing, however, that other factors potentially contributing to cellular accumulation of rhodamine 123, including mitochondrial membrane potential or expression of the efflux transporter P‐glycoprotein, have also to be considered.     

Interrater reliability study of cerebral palsy diagnosis, neurological subtype, and gross motor function

Aim To evaluate the interrater reliability of the inclusion in registries and classification of children with cerebral palsy (CP). Method Two studies were conducted. In study 1, 12 paediatricians from 11 countries viewed video sequences of 12 children with or without CP (nine males, three females; median age 6y; range 2-16). In study 2, 19 professionals from eight countries participated in an online exercise. They had to classify the same children but based on written vignettes. All participants had to evaluate whether the child had CP, the neurological subtype (Surveillance of Cerebral Palsy in Europe classification system), and gross motor function level (Gross Motor Function Classification System [GMFCS]). Kappa (κ) coefficients were calculated for categorical variables and intraclass correlation coefficients (ICCs) for ordinal data. Results Reliability was excellent in assessing whether or not a child had CP in study 1 (κ=1.00) and substantial in study 2 (κ=0.73); 95% confidence interval [CI] 0.58-0.87). For the neurological subtype, overall κ between paediatricians was 0.85 (95% CI 0.68-0.98), with full agreement observed for eight children. In study 2, overall κ was 0.78 (95% CI 0.61-0.91) with full agreement seen for five children. For the GMFCS, the ICC was 0.88 (95% CI 0.78-0.95) in study 1 and 0.80 (95% CI 0.64-0.91) in study 2. Interpretation Reliability was excellent for all characteristics classified by paediatricians viewing the videos and substantial for professionals reading vignettes.     

Neonatal Cutis Laxa and Hypertrichosis Lanuginosa in Sotos Syndrome

We report a case of transient neonatal cutis laxa and hypertrichosis lanuginosa as an initial presentation in Sotos syndrome. Little is known about skin involvement in Sotos syndrome. Our observation highlights that Sotos syndrome is a rare cause of cutis laxa and suggests that it is a useful neonatal skin clue to the diagnosis of overgrowth syndromes.