Deep phenotyping tools for characterizing preclinical morphological conditions are important for supporting genetic research studies. Objectives of this retrospective, cross-sectional, methods comparison study were to describe and compare qualitative and quantitative deep phenotypic characteristics of lumbosacral stenosis in Labrador retrievers using computed tomography (CT). Lumbosacral CT scans and medical records were retrieved from data archives at three veterinary hospitals. Using previously published qualitative CT diagnostic criteria, a board-certified veterinary radiologist assigned dogs as either lumbosacral stenosis positive or lumbosacral stenosis negative at six vertebral locations. A second observer independently measured vertebral canal area, vertebral fat area, and vertebral body area; and calculated ratios of vertebral canal area/vertebral body area and vertebral fat area/vertebral body area (fat area ratio) at all six locations. Twenty-five dogs were sampled (lumbosacral stenosis negative, 11 dogs; lumbosacral stenosis positive, 14 dogs). Of the six locations, cranial L6 was the most affected by lumbosacral stenosis (33%). Five of six dogs (83%) with clinical signs of lumbosacral pain were lumbosacral stenosis positive at two or more levels. All four quantitative variables were significantly smaller at the cranial aspects of the L6 and L7 vertebral foramina than at the caudal aspects (P< 0.0001). Fat area ratio was a significant predictor of lumbosacral stenosis positive status at all six locations with cranial L6 having the greatest predictive value (R = 0.43) and range of predictive probability (25-90%). Findings from the current study supported the use of CT as a deep phenotyping tool for future research studies of lumbosacral stenosis in Labrador retrievers.

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Objective Alzheimer’s disease (AD) is a neurodegenerative disease characterized by Aβ plaques in the brain. The aim of this study was to evaluate the effectiveness of a novel radiotracer, 4-[11C]methylamino-4′-N,N-dimethylaminoazo-benzene ([11C]TAZA), for binding to Aβ plaques in postmortem human brain (AD and normal control (NC)). Methods Radiosyntheses of [11C]TAZA, related [11C]Dalene (11C-methylamino-4′-dimethylaminostyrylbenzene), and reference [11C]PIB were carried out using [11C]methyltriflate prepared from [11C]CO2 and purified using HPLC. In vitro binding affinities were carried out in human AD brain homogenate with Aβ plaques labeled with [3H]PIB. In vitro autoradiography studies with the three radiotracers were performed on hippocampus of AD and NC brains. PET/CT studies were carried out in normal rats to study brain and whole body distribution. Results The three radiotracers were produced in high radiochemical yields (>40%) and had specific activities >37 GBq/μmol. TAZA had an affinity, Ki = 0.84 nM and was five times more potent than PIB. [11C]TAZA bound specifically to Aβ plaques present in AD brains with gray matter to white matter ratios >20. [11C]TAZA was displaced by PIB (>90%), suggesting similar binding site for [11C]TAZA and [11C]PIB. [11C]TAZA exhibited slow kinetics of uptake in the rat brain and whole body images showed uptake in interscapular brown adipose tissue (IBAT). Binding in brain and IBAT were affected by preinjection of atomoxetine, a norepinephrine transporter blocker. Conclusion [11C]TAZA exhibited high binding to Aβ plaques in human AD hippocampus. Rat brain kinetics was slow and peripheral binding to IBAT needs to be further evaluated.

BackgroundCanine lumbosacral stenosis is defined as narrowing of the caudal lumbar and/or sacral vertebral canal. A risk factor for neurologic problems in many large sized breeds, lumbosacral stenosis can also cause early retirement in Labrador retriever military working dogs. Though vital for conservative management of the condition, early detection is complicated by the ambiguous nature of clinical signs of lumbosacral stenosis in stoic and high-drive Labrador retriever military working dogs. Though clinical diagnoses of lumbosacral stenosis using CT imaging are standard, they are usually not performed unless dogs present with clinical symptoms. Understanding the underlying genomic mechanisms would be beneficial in developing early detection methods for lumbosacral stenosis, which could prevent premature retirement in working dogs. The exomes of 8 young Labrador retriever military working dogs (4 affected and 4 unaffected by lumbosacral stenosis, phenotypically selected by CT image analyses from 40 dogs with no reported clinical signs of the condition) were sequenced to identify and annotate exonic variants between dogs negative and positive for lumbosacral stenosis.ResultsTwo-hundred and fifty-two variants were detected to be homozygous for the wild allele and either homozygous or heterozygous for the variant allele. Seventeen non-disruptive variants were detected that could affect protein effectiveness in 7 annotated (SCN1B, RGS9BP, ASXL3, TTR, LRRC16B, PTPRO, ZBBX) and 3 predicted genes (EEF1A1, DNAJA1, ZFX). No exonic variants were detected in any of the canine orthologues for human lumbar spinal stenosis candidate genes.ConclusionsTTR (transthyretin) gene could be a possible candidate for lumbosacral stenosis in Labrador retrievers based on previous human studies that have reported an association between human lumbar spinal stenosis and transthyretin protein amyloidosis. Other genes identified with exonic variants in this study but with no known published association with lumbosacral stenosis and/or lumbar spinal stenosis could also be candidate genes for future canine lumbosacral stenosis studies but their roles remain currently unknown. Human lumbar spinal stenosis candidate genes also cannot be ruled out as lumbosacral stenosis candidate genes. More definitive genetic investigations of this condition are needed before any genetic test for lumbosacral stenosis in Labrador retriever can be developed.Electronic supplementary materialThe online version of this article (10.1186/s40575-017-0052-6) contains supplementary material, which is available to authorized users.

Phenotypic and genotypic characterization of lumbosacral stenosis in Labrador retrievers Meenakshi Mukherjee Lumbosacral stenosis (LS) is a structural narrowing of the spinal canal in the canine lumbosacral spine. Large-sized working and sporting dog breeds such as Labrador retrievers are predisposed for reasons that are incompletely understood. The narrowing of spinal canal observed in LS can cause compression of underlying meningeal, neural and vascular tissues, which in turn can lead to clinical symptoms like lower back pain, Labrador retrievers that might become working dogs can significantly improve the procurement process. And if reasons behind early occurrence of LS were premature degenerative changes instead, early detection would mean preventative conditioning training protocols and better therapeutic treatments. However, it is important to note that LS is not restricted to working dogs (young and old) alone, the disease also appears in non-working dogs (more commonly in older dogs). But, early detection of LS would improve the quality of life of Labrador retrievers-both working and non-working that might be affected by LS. It would also be beneficial for the agencies that employ and have financial stakes in these dogs. v DEDICATION This document marks the completion of a nearly four-and-a-half-year long project towards a doctoral degree in genetics. None of this would have been possible without the love and support from the two most important people in my life-my parents. I would like to thank them both from the bottom of my heart for all the sacrifices that they have made over the years, making it possible for me to be where I am today. I share the honor of this degree with both of them. I owe who I am today-as a person and as an academic-to the values that they instilled in me. I would also like to acknowledge all the friends I have made throughout my life-you all have shown me love, loyalty and support. I am a better individual today for having known all of you and I am extremely grateful that you all chose me to be your friend. And last but not the least (even though she will be unable to read this), I would like to thank my best friend and loving loyal companion Maggie, for always being present with unconditional love and support. vi ACKNOWLEDGEMENT I would first like to thank all my committee members for their guidance throughout this project-both with experimental design and implementation of the study.