Genetic analysis of the hypothalamic neurotensin system

Neurotensins and their therapeutic potential: research field study

The natural tridecapeptide neurotensin has been emerged as a promising therapeutic scaffold for the treatment of neurological diseases and cancer. In this work, we aimed to identify the top 100 most cited original research papers as well as recent key studies related to neurotensins. The Web of Science Core Collection database was searched and the retrieved research articles were analyzed by using the VOSviewer software. The most cited original articles were published between 1973 and 2013. The top-cited article was by Carraway and Leeman reporting the discovery of neurotensin in 1973. The highly cited terms were associated with hypotension and angiotensin-converting-enzyme. The conducted analysis reveals the therapeutic potentials of neurotensin, and further impactful research toward its clinical development is warrantied.

Microarray‑based identification of nerve growth‑promoting genes in neurofibromatosis type I

As a genetic disease, neurofibromatosis type 1 (NF1) is characterized by abnormalities in multiple tissues derived from the neural crest, including neoplasms in the ends of the limbs. The exact mechanism of nerve growth in NF1 is unclear. In the present study, the gene expression profile of nerves in healthy controls and NF1 patients with macrodactylia of the fingers or toes were analyzed in order to identify possible genes associated with nerve growth. The Whole Human Genome Microarray was selected to screen for different gene expression profiles, and the result was analyzed with Feature Extraction software. The target genes were verified at the transcriptional and translational levels by reverse transcription‑polymerase chain reaction and western blotting, respectively. A common set of 28 genes were identified to be changed >5‑fold in the NF1 patients compared with the healthy controls. Among them, the metastasis‑associated genes, lymphocyte function‑associated antigen 1, C‑X‑C chemokine receptor type 4 and intracellular adhesion molecule 1, and the inflammatory cytokines, interleukin (IL) 1β, IL‑6 and IL‑8, were downregulated significantly. Mainly genes that changed >10‑fold were analyzed in this study, and HOXC8 demonstrated activity in promoting nerve growth. Through the analysis of the mRNA expression of the nerves in the NF1 patients, target molecules contributing to nerve growth during NF1 development were investigated, which aided in improving our understanding of this disease, and may provide a novel direction for nerve repair and regeneration.

Evidence for genes on chromosome 2 contributing to alcohol dependence with conduct disorder and suicide attempts

Twin studies provide strong evidence that there is a shared genetic liability that predisposes to a number of different psychiatric outcomes related to behavioral disinhibition. Further, alcohol dependence comorbid with other disinhibitory disorders is particularly heritable. Chromosome 2p14-2q14.3 has been linked to multiple psychiatric conditions related to behavioral undercontrol. In the Collaborative Study on the Genetics of Alcoholism (COGA), we previously reported linkage to this region with alcohol dependence (AD), suicide attempts (SUI), and conduct disorder (CD). In this study, we follow-up on these previous reports of linkage by combining the phenotypes in analyses that jointly consider the presence of multiple conditions. Linkage analyses of the combined phenotype of AD with CD or SUI results in a maximum LOD score of 5.4 in this region. In addition to this primary linkage peak, independent samples have reported linkage to other alcohol-related phenotypes across chromosome 2. Accordingly, we followed-up these linkage signals by testing for association with SNPs across chromosome 2 in a case-control sample, in which a subset of the cases consisted of alcohol-dependent probands from the linkage sample. We find evidence of association with the combined AD with CD or SUI phenotype, with 23 genes surviving permutation testing. The number of associated genes across the chromosome may explain the persistent linkage findings reported on chromosome 2 across a number of independent studies of alcohol and disinhibitory phenotypes. Further, none of the genes were located directly under the primary COGA linkage peak, which has implications for association tests following-up linkage peaks.

Genetic regulation of hypothalamic cocaine and amphetamine-regulated transcript (CART) in BxD inbred mice

Cocaine and Amphetamine-Regulated Transcript (CART) peptides are implicated in a wide range of behaviors including in the reinforcing properties of psychostimulants, feeding and energy balance and stress and anxiety responses. We conducted a complex trait analysis to examine natural variation in the regulation of CART transcript abundance (CARTta) in the hypothalamus. CART transcript abundance was measured in total hypothalamic RNA from 26 BxD recombinant inbred (RI) mouse strains and in the C57BL/6 (B6) and DBA/2J (D2) progenitor strains. The strain distribution pattern for CARTta was continuous across the RI panel, which is consistent with this being a quantitative trait. Marker regression and interval mapping revealed significant quantitative trait loci (QTL) on mouse chromosome 4 (around 58.2 cM) and chromosome 11 (between 20-36 cM) that influence CARTta and account for 31% of the between strain variance in this phenotype. There are numerous candidate genes and QTL in these chromosomal regions that may indicate shared genetic regulation between CART expression and other neurobiological processes referable to known actions of this neuropeptide.

Neurotensin agonists: potential in the treatment of schizophrenia

Neurotensin (NT) is a neuropeptide that, for decades, has been implicated in the biology of schizophrenia. It is closely associated with, and is thought to modulate, dopaminergic and other neurotransmitter systems involved in the pathophysiology of various neuropsychiatric diseases, including schizophrenia. This review outlines the neurochemistry and function of the NT system and the data implicating its role in schizophrenia. The data suggest that NT receptor agonists have the potential to be used as novel therapeutic agents for the treatment of schizophrenia, with the added benefits of (i) not causing weight gain, an adverse effect that is problematic with some of the currently used atypical antipsychotic drugs; and (ii) helping patients to stop smoking, a behaviour that is highly prevalent in those with schizophrenia.

Confirmation of quantitative trait loci for ethanol sensitivity and neurotensin receptor density in crosses derived from the inbred high and low alcohol sensitive selectively bred rat lines

RATIONALE

Genetically influenced alcohol sensitivity is thought to be an important risk factor for the development of alcoholism. An effective first step for identifying genes that mediate variation in alcohol sensitivity is through quantitative trait loci (QTL) mapping in model organisms.

OBJECTIVE

Fourteen provisional QTLs related to alcohol sensitivity were previously mapped in an F2 derived from the IHAS1 and ILAS1 rat lines. The objective of the current study was to confirm those QTLs in an independently derived F2 and in congenics that were bred for two of the loci.

MATERIALS AND METHODS

IHAS1 X ILAS1 F2 (n=450) were tested for alcohol-induced loss of righting reflex (LORR), blood ethanol concentration at regain of righting reflex (BECRR), sensitivity and acute tolerance on the Rotarod, and neurotensin receptor density (NTR1). Rats were genotyped at the 14 candidate loci and QTL mapping was conducted. Reciprocal congenic strains were bred for loci on chromosomes 2 and 5 and tested for LORR and BECRR.

RESULTS

Four LORR QTLs were mapped at the suggestive or significant level (chromosomes 2, 5, 12, and 13). BECRR was mapped to chromosomes 5, 12, and 13 either in the original or current experiment. Results of the congenic experiment also support QTLs for LORR and BECRR on chromosomes 2 and 5. QTLs for NTR1 density and behavior on the Rotarod were not confirmed.

CONCLUSIONS

QTL mapping in crosses derived from the IHAS1 and ILAS1 has successfully identified loci related to alcohol sensitivity. Recombinant congenics are now being bred to more finely map the confirmed QTLs.