Research Interests

The major aim of my laboratory is to understand the way the nervous system controls behavior.  We now know that the "simple nervous system" of the nematode Ascaris has much more complexity than was ever imagined--the chemical signaling system it uses are very diverse, and we are sorting them out. These signaling systems include the neuropeptides, which we are devoting a major effort towards identifying and sequencing; other signaling systems that we have worked on include serotonin and glutamate, both of which play an important role in the motor nervous system. These signaling systems typically are involved in the process of neuromodulation, and each chemical involved affects the system in a different way.  Some produce profound effects on the neurons they influence, and others have subtle effects. Different chemicals affect different subsets of neurons. Neuromodulation is a matter of details, but the details matter.

We are developing new techniques for identifying peptides in a complex mixture.  I am currently excited about a new class of antibodies that we are developing.  These are generic antibodies that recognize specific C-terminal dipeptide sequences, and we have found many new types of neurons that contain peptides recognized by these antibodies, implying that they contain novel peptides.  We are also using MALDI-TOF mass spectroscopy to search for new classes of neuropeptides.  The most significant advance this year has been the use of dissected nervous tissue from single worms as the immediate target in the mass spectrometer.  This has provided amazing sensitivity and specificity, and several new peptides have been detected and sequenced.  We are now raising antibodies to study their cellular localization.  The overall conclusion we have reached is that there is a large number of as-yet undescribed peptides in Ascaris. We have also successfully implemented for the first time in Ascaris an in-situ hybridization method, and have determined the location of the transcripts of 5 peptide-encoding genes. 

One recent result that we think is of profound importance is that although the neurons of Ascaris and C. elegans are morphologically the same (C. elegans is a miniature version of Ascaris), and although many of the neuropeptides found or predicted from gene sequences are identical or very similar in the 2 species, the cells in which the peptides are expressed are almost completely different.  We used 3 techniques (in situ hybridization, immunocytochemistry and mass spectrometry) to detect peptide expression in Ascaris, and obtained congruent results with each technique.  Expression of peptide encoding genes in C. elegans has been reported using GFP constructs.  Out of 16 cellular comparisons, 15 are different.  Only one neuron so far has shown the same peptide expression in the 2 species.  We conclude that the cellular expression pattern of peptides may be an important part of the way a nearly identical structure can produce different behavior.

Courses:

Zoology 152 - Introductory Biology
Zoology 523 - Neurobiology

Graduate students currently supervised:

India Viola, Zoology MS candidate. (irviola@wisc.edu)
    Working on cloning Ascaris neuropeptide gene-encoding transcripts and performing in-situ hybridization

Christopher Konop,  MS candidate (Zoology) 
    Antibodies against Ascaris neuropeptides

Jessica Jarecki,  PhD candidate (Neuroscience) 
    Mass spectrometry and gene arrays of Ascaris neuropeptides

Students supervised who recently earned graduate degrees:

Gaoussou Diarra, PhD.  2006.  (Zoology)
    Zoology - Using phage-display antibodies to isolate new peptide immunoreactivities.

Jennifer Cho, PhD. 2oo4. (Neuroscience)
    “Molecular Biological Analysis of Neuropeptide Gene Transcripts from the Nematode Ascaris suum”

Joanne Yew, PhD. 2003. (Neuroscience)
    “Characterization of Neuropeptides in Ascaris suum Using Mass Spectrometry”

Ivan Chevere, PhD. 2002.
    Neuropeptide study in Ascaris by immunocytochemical and molecular biology methods. Abstract.

Selected Publications

• Yew, J.Y., Davis, R., Dikler, S.,Nanda, J., Reinders, B., and Stretton, A.  (2007) Products of the afp-6 gene of the nematode Ascaris suum have different biological actions.  J Comp. Neurol. In press

• Yew, JY, Davis R, Dikler S, Nanda J, Reinders B, and Stretton AO (2006) Identification, cellular localization, and physiological activity of neuropeptides AF21, 22, and 23, the products of the afp-6 transcript in the nematode Ascaris suum. Completed MS

• Yew, J.Y., Kutz, K.K., Dikler, S., Messinger, L., Li. L., and Stretton, A.O. (2005) A mass spectrometric map of neuropeptide expression in Ascaris suum. J Comp. Neurol. In

• Chevere, I., Donmoyer, J.E., and Stretton, A.O.W. Cellular localization of AF17, a FMRFamide-like peptide with CCK-like immunoreactivity, in the nervous system of the nematode Ascaris suum. J. Comp. Neurol. J. Comp. Neurol. Under revision.

• Sithigorngul, P., and Stretton, A.O.W. Localization of AF1 and AF1-like Peptides in the Nervous System of the nematode Ascaris suum with Specific Monoclonal Antibodies; Different Expression Patterns of AF1 in A. suum and Caenorhabditis elegans. J. Comp. Neurol. Under revision.

• Sithigorngul, P., and Stretton, A.O.W. Under revision. Isolation of a peptide present in a single neuron of the nematode Ascaris suum.

• Chevere, I., Donmoyer, J.E., and Stretton, A.O.W. Under revision. Cellular localization of AF17, a FMRFamide-like peptide with CCK-like immunoreactivity, in the nervous system of the nematode Ascaris suum. J. Comp. Neurol.

• Stretton, AOW. 2002. The first sequence: Fred Sanger and Insulin. Genetics 162: 527-532.

• Angstadt, J.D., Donmoyer, J.D., and Stretton, A.O.W. 2001. A study of dendritic spines in the nematode Ascaris highlights the advantages and limitations of anatomical methods in identifying functional synaptic interactions. J. Comp. Neurol. 432: 512-527.

• Davis, R.E., and Stretton, A.O.W. 2001. Structure-activity relationships of 18 endogenous neuropeptides on the motornervous system of the nematode Ascaris suum. Peptides. 22: 7-23.

• Reinitz, C.A., Herfel, H.G., Messinger, L.A., and Stretton, A.O.W. 2000. Changes in locomotory behavior and cAMP produced in Ascaris suum by neuropeptides from Ascaris or C. elegans. Mol. Biochem. Parasitol. 111: 185-197.