Rab GTPases including Rab27a, Rab38 and Rab32 function in melanosome maturation or trafficking in melanocytes. A screen to identify additional Rabs involved in these processes revealed the localization of GFP-Rab17 on recycling endosomes (REs) and melanosomes in melanocytic cells. Rab17 mRNA expression is regulated by microphthalmia transcription factor (MITF), a characteristic of known pigmentation genes. Rab17 siRNA knockdown in melanoma cells quantitatively increased melanosome concentration at the cell periphery. Rab17 knockdown did not inhibit melanosome maturation nor movement, but it caused accumulation of melanin inside cells. Double knockdown of Rab17 and Rab27a indicated that Rab17 acts on melanosomes downstream of Rab27a. Filopodia are known to play a role in melanosome transfer, and in Rab17 knockdown cells filopodia formation was inhibited. Furthermore, we show that stimulation of melanoma cells with α-melanocytestimulating hormone induces filopodia formation, supporting a role for filopodia in melanosome release. Cell stimulation also caused redistribution of REs to the periphery, and knockdown of additional RE-associated Rabs 11a and 11b produced a similar accumulation of melanosomes and melanin to that seen after loss of Rab17. Our findings reveal new functions for RE and Rab17 in pigmentation through a distal step in the process of melanosome release via filopodia.

Vascular immune-inflammatory responses play a crucial role in the progression and outcome of atherosclerosis. The ability to assess localized inflammation through detection of specific vascular inflammatory biomarkers would significantly improve cardiovascular risk assessment and management; however, no multi-parameter molecular imaging technologies have been established to date. Here, we report the targeted in vivo imaging of multiple vascular biomarkers using antibody-functionalized nanoparticles and surface-enhanced Raman scattering (SERS).Methods: A series of antibody-functionalized gold nanoprobes (BFNP) were designed containing unique Raman signals in order to detect intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and P-selectin using SERS.Results: SERS and BFNP were utilized to detect, discriminate and quantify ICAM-1, VCAM-1 and P-selectin in vitro on human endothelial cells and ex vivo in human coronary arteries. Ultimately, non-invasive multiplex imaging of adhesion molecules in a humanized mouse model was demonstrated in vivo following intravenous injection of the nanoprobes.Conclusion: This study demonstrates that multiplexed SERS-based molecular imaging can indicate the status of vascular inflammation in vivo and gives promise for SERS as a clinical imaging technique for cardiovascular disease in the future.

Most of the existing algorithms for approximate Bayesian computation (ABC) assume that it is feasible to simulate pseudo-data from the model at each iteration. However, the computational cost of these simulations can be prohibitive for high dimensional data. An important example is the Potts model, which is commonly used in image analysis. Images encountered in real world applications can have millions of pixels, therefore scalability is a major concern. We apply ABC with a synthetic likelihood to the hidden Potts model with additive Gaussian noise. Using a pre-processing step, we fit a binding function to model the relationship between the model parameters and the synthetic likelihood parameters. Our numerical experiments demonstrate that the precomputed binding function dramatically improves the scalability of ABC, reducing the average runtime required for model fitting from 71 hours to only 7 minutes. We also illustrate the method by estimating the smoothing parameter for remotely sensed satellite imagery. Without precomputation, Bayesian inference is impractical for datasets of that scale.Comment: 5th IMS-ISBA joint meeting (MCMSki IV