Locus Heterogeneity for Waardenburg Syndrome is Predictive of Clinical Subtypes

Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between −2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3.     

Repeated Recent Aggressive Encounters Do Not Affect Behavioral Consistency in Male Siamese Fighting Fish

Consistent individual differences in behavior suggest that individuals respond in a predictable and repeatable manner in a specific situation while differing from other individuals. Male Siamese fighting fish exhibit consistent individual differences in decision‐making strategies when they encounter a receptive female and a rival male simultaneously. However, whether these differences are altered by recent experience is unknown. We examined the influence of repeated aggressive encounters on behavioral consistency and decision‐making. Males were presented with paired female–male dummies prior to any aggressive experiences to obtain a baseline measure. Next, males either won or lost three consecutive contests against rivals and then received the paired female–male dummies after each of these encounters. Overall levels of highly aggressive behaviors were affected by contest outcome, while levels of female‐directed were not. Not surprisingly, winning a fight led to an increase in male‐directed bites, an overtly aggressive behavior that only occurs after fights have escalated. Fighting a male before encountering the dummies caused males to perform more tail beats to the dummy male, perhaps as a result of increased motivation. Males exhibited similar levels of repeatability and used the same strategies when faced with conflicting stimuli regardless of fighting experience. Thus, while winning or losing a fight impacts overall aggression, it does not influence behavioral consistency. This study demonstrates that consistent individual differences and decision‐making strategies may be resistant to recent aggressive experiences, even over a period of days.     

Uridine phosphorylase activity among the class mollicutes

Uridine phosphorylase activity has been used to detect mycoplasmas in cell cultures by measuring formation of¹⁴C-uracil from¹⁴C-uridine. In this report we show that all species ofMycoplasma, Acholeplasma, andUreaplasma tested exhibited uridine phorphorylase activity. Among the genusSpiroplasma, serogroups I-1, I-3, I-5, I-7, I-8, IV, XIII, and XIV lacked uridine phosphorylase activity.Present address: Ciba-Geigy, Basel, Switzerland.     

AFM imaging of protein movements: histone H2A-H2B release during nucleosome remodeling

Being able to follow assembly/disassembly reactions of biomolecular complexes directly at the single molecule level would be very useful. Here, we use an AFM technique that can simultaneously obtain topographic images and identify the locations of a specific type of protein within those images to monitor the histone H2A component of nucleosomes acted on by human Swi-Snf, an ATP-dependent nucleosome remodeling complex. Activation of remodeling results in significant H2A release from nucleosomes, based on recognition imaging and nucleosome height changes, and changes in the recognition patterns of H2A associated directly with hSwi-Snf complexes.     

Computational Modelling of Metastasis Development in Renal Cell Carcinoma

The biology of the metastatic colonization process remains a poorly understood phenomenon. To improve our knowledge of its dynamics, we conducted a modelling study based on multi-modal data from an orthotopic murine experimental system of metastatic renal cell carcinoma. The standard theory of metastatic colonization usually assumes that secondary tumours, once established at a distant site, grow independently from each other and from the primary tumour. Using a mathematical model that translates this assumption into equations, we challenged this theory against our data that included: 1) dynamics of primary tumour cells in the kidney and metastatic cells in the lungs, retrieved by green fluorescent protein tracking, and 2) magnetic resonance images (MRI) informing on the number and size of macroscopic lesions. Critically, when calibrated on the growth of the primary tumour and total metastatic burden, the predicted theoretical size distributions were not in agreement with the MRI observations. Moreover, tumour expansion only based on proliferation was not able to explain the volume increase of the metastatic lesions. These findings strongly suggested rejection of the standard theory, demonstrating that the time development of the size distribution of metastases could not be explained by independent growth of metastatic foci. This led us to investigate the effect of spatial interactions between merging metastatic tumours on the dynamics of the global metastatic burden. We derived a mathematical model of spatial tumour growth, confronted it with experimental data of single metastatic tumour growth, and used it to provide insights on the dynamics of multiple tumours growing in close vicinity. Together, our results have implications for theories of the metastatic process and suggest that global dynamics of metastasis development is dependent on spatial interactions between metastatic lesions.     

P-selectin and CD63 use different mechanisms for delivery to Weibel-Palade bodies

The biogenesis of endothelial-specific Weibel-Palade bodies (WPB) is poorly understood, despite their key role in both haemostasis and inflammation. Biogenesis of specialized organelles of haemopoietic cells is often adaptor protein complex 3-dependent (AP-3-dependent), and AP-3 has previously been shown to play a role in the trafficking of both WPB membrane proteins, P-selectin and CD63. However, WPB are thought to form at the trans Golgi network (TGN), which is inconsistent with a role for AP-3, which operates in post-Golgi trafficking. We have therefore investigated in detail the mechanisms of delivery of these two membrane proteins to WPB. We find that P-selectin is recruited to forming WPB in the trans-Golgi by AP-3-independent mechanisms that use sorting information within both the cytoplasmic tail and the lumenal domain of the receptor. In contrast, CD63 is recruited to already-budded WPB by an AP-3-dependent route. These different mechanisms of recruitment lead to the presence of distinct immature and mature populations of WPB in human umbilical vein endothelial cells (HUVEC).     

Distinct CDR3 conformations in TCRs determine the level of cross-reactivity for diverse antigens, but not the docking orientation

T cells are known to cross-react with diverse peptide MHC Ags through their alphabeta TCR. To explore the basis of such cross-reactivity, we examined the 2C TCR that recognizes two structurally distinct ligands, SIY-K(b) and alloantigen QL9-L(d). In this study we characterized the cross-reactivity of several high-affinity 2C TCR variants that contained mutations only in the CDR3alpha loop. Two of the TCR lost their ability to cross-react with the reciprocal ligand (SIY-K(b)), whereas another TCR (m67) maintained reactivity with both ligands. Crystal structures of four of the TCRs in complex with QL9-L(d) showed that CDR1, CDR2, and CDR3beta conformations and docking orientations were remarkably similar. Although the CDR3alpha loop of TCR m67 conferred a 2000-fold higher affinity for SIY-K(b), the TCR maintained the same docking angle on QL9-L(d) as the 2C TCR. Thus, CDR3alpha dictated the affinity and level of cross-reactivity, yet it did so without affecting the conserved docking orientation.