Stefan Maas, Ph.D.
Assistant Professor
Molecular Biology

Phone: 610-758-6276
Email: swm3@lehigh.edu

Research Summary

Our lab is interested in understanding the molecular basis for the tremendous complexity and diversity of higher organisms. This complexity is based on the number of different gene products available for structural, enzymatic and regulatory functions. Recently, whole-genome sequencing of a diverse set of species from primitive to highly developed organisms (bacteria, yeast, worm, fly, fish, mouse, human) has demonstrated that during evolution the number of building blocks (genes) in genomes, has not increased at the same rate as the observed organismic complexity (for example: fruit fly 13,000 genes, homo sapiens ca. 30,000 genes). This unexpected finding underscores the important role of post-transcriptional and post-translational mechanisms for the generation of protein diversity.

We are focusing on a recently discovered phenomenon of pre-mRNA modification, called RNA editing. In general, the term RNA editing is used to describe the posttranscriptional alteration of gene sequences by different mechanisms including the deletion, insertion and modification of nucleotides. Base changes in codons often lead to amino acid changes and result in alteration of protein function.
In mammals, the modification of adenosines (A) to inosine (I) appears to be particularly widespread and is known to regulate crucial functional properties of neurotransmitter receptors in the brain. Since inosine acts as guanosine during translation it can change the readout of edited codons. The coexpression of edited and unedited protein variants in the same cell can increase exponentially the number of gene products generated from a single gene. A-to-I RNA editing is catalyzed by the ADAR (adenosine deaminase acting on RNA) family of enzymes and these proteins recognize a double-stranded RNA structure formed from exonic and intronic sequences within the substrate molecule.

In addition to the recoding of mRNA information, the modification of RNAs by ADARs could potentially affect any biological process that involves sequence- or structure-specific interactions with RNA.

We use molecular biological, biochemical and genetics approaches to study how prevalent A-to-I RNA editing is in the transcriptome and how it is regulated. Furthermore, we investigate the consequences of misregulation of or deficiency in RNA editing and how it can contribute to pathophysiological processes.

Recent Publications

Gommans, W.M., and Maas, S., 2008: Characterization of ADAR1-mediated modulation of gene expression. *BBRC*; 377(1):170-5 published online October 7, 2008

Maas, S., and Gommans, W.M. 2008: Novel exon of mammalian ADAR2 extends open reading frame. *PLoS ONE*; in press

Gommans, W.M., Tatalias, N.E., Sie, C., Dupuis, D.E., Vendetti, N.J., Smith, L., Kaushal, R., and Maas, S., 2008: Screening of human SNP database identifies recoding sites of A-to-I RNA editing. RNA, 14: 10, published online September 4, 2008

Orlowski, R.J., O'Rourke, K.S., Olorenshaw, I.,  Hawkins, G.A., Maas, S., and Laxminarayana, D., 2008: Altered Editing in Cyclic Nucleotide Phosphodiesterase 8A1 (PDE8A1) Gene Transcripts of Systemic Lupus Erythematosus (SLE) T Lymphocytes. Immunology, published online May 7, 2008

Wynne, R.D., Maas, S., and Saldanha, C.J., 2008: Molecular characterization of the injury-induced aromatase transcript in the adult zebra finch brain. J Neurochem., 105: 1613-1624

Gommans, W.M., Dupuis, D.E., McCane, J.E., Tatalias, N.E., and Maas, S., 2008: Diversifying Exon Code through A-to-I RNA Editing. In: DNA and RNA Editing: Mechanisms and Functions; Wiley publishers; edited by: Harold Smith, pp3-30

Laxminarayana, D., O'Rourke, K.S., Maas, S.,  and Olorenshaw, I., 2007: Altered Editing in RNA editing Adenosine Deaminase ADAR2 Gene Transcripts of Systemic Lupus Erythematosus (SLE) T   Lymphocytes. Immunology, 121(3):359-69

Maas, S., Kawahara, Y., Tamburro, K.M., and Nishikura, K. 2006: A-to-I RNA editing and human disease. RNA Biology, 3(1) e1-9. PDF
Listen to the abstract!

Koeris, M., Funke, L., Shrestha, J., Rich. A., and Maas , S. 2005: Modulation of ADAR1 editing activity by Z-RNA in vitro. Nucleic Acids Res., 33 (16): 5362-70. PDF

Athanasiadis, A., D. Placido, S. Maas, B.A. Brown, 2nd, K. Lowenhaupt, and A. Rich , 2005: The crystal structure of the Zbeta domain of the RNA-editing enzyme ADAR1 reveals distinct conserved surfaces among Z-domains . J Mol Biol , 351 (3): 496-507. PDF

Athanasiadis, A., Rich, A., and Maas, S. 2004: Widespread A-to-I RNA editing of Alu-containing mRNAs in the human transcriptome. PLoS Biology, 2 (12) e391 PDF

Luciano, D.J., Mirsky, H., Vendetti, N.J., and Maas, S., 2004: RNA editing of a miRNA precursor. RNA,10(8):1174-1177 PDF

Tsibris, J.C.M., Maas, S., Segars, J.H., Nicosia, S.V., Enkemann, S.A., O'Brien, W.F., and Spellacy, W.N. 2003: New potential regulators of uterine leiomyomata from DNA arrays: The ionotropic glutamate receptor GluR2. Biochem Biophys Res Commun, 312, 249-254 PDF

Maas, S., Rich, A., and Nishikura, K., 2003: A-to-I RNA editing: recent news and remaining mysteries. J.Biol.Chem. 278 (3) 1391-4 PDF

Maas, S., Patt, S., Schrey, M., and Rich, A., 2001: Underediting of GluR-B mRNA in malignant gliomas. Proc. Natl. Acad. Sci. 98 (25), 14687-14692 PDF (see also: Editor's choice in Science Dec. 14, 2001 and in MIT TechTalk)

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