Effects of androgen receptor polyglutamine tract expansion on proliferation of NG108-15 cells

Molecular diagnosis of neurogenetic disorders involving trinucleotide repeat expansions

There are more than 15 known neurogenetic disorders involving trinucleotide repeat expansion. Expanded repeats range from small expansions of 20-100 copies to larger expansions of up to several thousand units. These dynamic expansions result in variability in age of onset, degree of severity and clinical presentation. Individuals carrying alleles in the intermediate range, known as premutation alleles, are often asymptomatic, but can potentially transmit a further expanded allele to his/her offspring. For autosomal dominant adult-onset disorders, carriers are asymptomatic prior to disease onset. With current molecular tools, it is now possible to determine the presence and number of expanded repeats for accurate diagnosis, presymptomatic testing and carrier status screening. This review examines some of the current approaches for molecular diagnosis and discusses the issues unique to triplet repeat diseases.

Cell Models for the Study of Sex Steroid Hormone Neurobiology

To date many aspects of neurons and glia biology remain elusive, due in part to the cellular and molecular complexity of the brain. In recent decades, cell models from different brain areas have been established and proven invaluable toward understanding this complexity. In the field of steroid hormone neurobiology, an important question is: what is the profile of steroid hormone receptor expression in these specific cell lines? Currently, a clear summary of such receptor profiling is lacking. For this reason, we summarized in this review the expression of estrogen, progesterone, and androgen receptors in several widely used cell lines (glial and neuronal) derived from the forebrain and midbrain, based on our own data and that from the literature. Such information will aid in the selection of specific cell lines used to test hypotheses related to the biology of estrogens, progestins, and/or androgens.

Androgen receptor and Kennedy disease/spinal bulbar muscular atrophy

Kennedy Disease/Spinal Bulbar Muscular Atrophy (KD/SBMA) is a progressive neurodegenerative disease caused by genetic polyglutamine expansion of the androgen receptor. We have recently found that overexpression of wildtype androgen receptor in skeletal muscle of transgenic mice results in a KD/SBMA phenotype. This surprising result challenges the orthodox view that KD/SBMA requires expression of polyglutamine expanded androgen receptor within motoneurons. Theories relating to the etiology of this disease drawn from studies of human patients, cellular and mouse models are considered with a special emphasis on potential myogenic contributions to as well as the molecular etiology of KD/SBMA.

A survey of trinucleotide/tandem repeat-containing transcripts (TNRTs) isolated from human spinal cord to identify genes containing unstable DNA regions as candidates for disorders of motor function

Expansion of unstable DNA regions containing trinucleotide/tandem repeats (TNRs) represents a common genetic mutation in hereditary forms of neurological disorders. The spectrum of neurological diseases linked to TNR expansions has recently broadened to include conditions with both dominant and recessive inheritance and those with or without clinical anticipation. In view of the frequent involvement of the spinal cord in neurodegenerative disorders, we have analysed this key tissue to identify pathological TNRs. We have used two approaches to isolate a wide range of trinucleotide/tandem repeat-containing transcripts (TNRTs) from human spinal cord, firstly a polymerase chain reaction (PCR)-based method and secondly by screening a spinal cord cDNA library immobilised on a membrane. Overall, 97 TNRTs belonging to a number of key protein families, the most highly represented being transcription factors, intracellular signalling molecules and cytoskeletal proteins, have been isolated most of which have not previously been considered as potential disease-causing genes. The commonest repeat motifs found in our study were CAG (37%) and CCG (24%). Known genes involved in DNA repeat expansion-related neurological disorders (e.g., AAD10, Ataxin-3, Huntingtin) were detected which validated our methods. We have characterised homogeneous TNRs among the detected gene candidates in a search for potential pathological repeat expansions. The potential role of the gene candidates identified is discussed in terms of their contribution to neurodegenerative processes.

Androgen induced cell death in SHSY5Y neuroblastoma cells expressing wild-type and spinal bulbar muscular atrophy mutant androgen receptors

Spinal bulbar muscular atrophy (SBMA) is one of a family of inherited neurodegenerative diseases caused by expansion of CAG encoding polyglutamine repeats; in SBMA the affected gene is the androgen receptor. To understand further the mechanisms that lead to neuronal cell death in SBMA, we generated SHSY5Y neuroblastoma cell lines that stably express identical levels of wild-type (19 polyglutamine repeat) or SBMA (52 polyglutamine repeat) androgen receptor. Parental SHSY5Y cells do not express detectable levels of the androgen receptor. In the absence of androgen, the transfected cell lines have similar phenotypes and growth characteristics to parental SHSY5Y cells. However, upon treatment with androgen, both cell lines undergo a marked dose-dependent loss of viability; this loss was significantly greater in cells expressing the SBMA receptor. Morphological analyses of the androgen treated cells revealed that cell death bore hallmarks of apoptosis involving altered nuclear morphology and cleavage of poly(ADP-ribose) polymerase and of caspase 3 in both wild-type and SBMA cell lines. The caspase inhibitor VAD-fmk was able to decrease loss of viability of both cell lines on exposure to androgen.