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Peter Baas

Peter Baas, PhD

Professor; Director, Graduate Program in Neuroscience

Department: Neurobiology & Anatomy


  • Postdoctoral Fellowship - Temple University
  • PhD - Michigan State University

Awards & Honors

  • Drexel Provost Award for Outstanding Scholarly Productivity – Career (2019)

Dr. Baas is a professor in the Department of Neurobiology & Anatomy at Drexel University College of Medicine. He is also director of the graduate program in neuroscience and an NIH-funded postdoctoral training program in the neurosciences.

Research Overview

Peter Baas, PhD, is interested in all aspects of the neuronal cytoskeleton, with a particular emphasis on the regulation of microtubules in developing neurons. In recent years, his interests have expanded to include the underlying mechanisms by which flaws in microtubule-related proteins contribute to neurodegenerative diseases. Baas is frequently invited to present his work at national and international symposia, and has been consistently funded for three decades by federal agencies (NIH, NSF, DOD) as well as private foundations with missions related to treating neurodegenerative diseases and nerve injury.

Lab Members

Senior Scientists:
Drs. Wenqian Yu and Liang Qiang

Postdoctoral Fellows:
Drs. Emanuela Piermarini and Qinghua Wang

Graduate Students:
Ankita Patil, Hemalatha Muralidharan, Philip Yates and Shrobona Guha

Visiting Students:
Alessia Niceforo, Şeyma Akarsu and Ilgın Isiltan

Research Interests

Role of microtubules in development, disease and injury of the nervous system


The mission of the Baas Laboratory is to elucidate the cellular and molecular mechanisms by which the microtubule arrays of the neuron are established and regulated during development, health, and disease.  Toward this end, the laboratory uses a variety of techniques including microscopic, biochemical, and molecular assays.

Baas laboratory research image, microtubule arrays of the neuron.

Microtubules form the infrastructure of eukaryotic cells, acting as both architectural elements and as railways for the transport of cytoplasmic constituents. To serve these functions, microtubules must be organized into a wide variety of configurations, ranging from the bipolar conformation of the mitotic spindle to the dense paraxial arrays that occupy elongated cellular processes. Thus an important question in cell biology is how different cell types organize their microtubules into these various configurations.  Neurons are terminally postmitotic cells that no longer organize their microtubules into mitotic spindles. Instead, the microtubules of the neuron are utilized for the formation of elongated processes termed axons and dendrites. These two types of processes contain dense arrays of paraxially-oriented microtubules, none of which are attached to the centrosome or any comparable structure. Despite this, the microtubules within these processes are highly organized with respect to their intrinsic polarity. In the axon, the microtubules are uniformly oriented with their plus-ends distal to the cell body of the neuron. In the dendrite, the microtubules are nonuniformly oriented with roughly similar numbers of microtubules of each orientation. These distinct microtubule patterns are essential for defining the cytoplasmic composition of each type of process, as well as for regulating morphological characteristics such as their relative lengths.   For almost twenty years, the central issue addressed by the Baas Laboratory has been to elucidate the molecules and mechanisms by which the microtubule arrays of the neuron are established during development.

Baas laboratory research image, microtubules in mitotic cells and neurons

One of the major conceptual breakthroughs came when it was established by the Baas Laboratory that neurons do not abandon the fundamental mechanisms that organize microtubules during mitosis. In the mitotic spindle, microtubule organization is orchestrated by a combination of the assembly properties of the microtubules together with forces generated on the microtubules by molecular motor proteins. The Baas Laboratory has established that this same general theme is true in neurons, and many of the very same proteins that organize microtubules in the mitotic spindle also do so in axons and dendrites.  In particular, many of the molecular motor proteins that had been assumed to be mitosis-specific continue to be expressed in neurons, where they play critical roles in orchestrating microtubules in axons, dendrites, axonal branches, and growth cones. 

Peter Baas laboratory research image, Molecular Motors Transport Short Microtubules

Most recently, the laboratory has put forward a model called “cut and run” in which the molecular motors can only transport microtubules if they are very short. If the microtubules are longer than just a few microns, then forces imposed upon them by the molecular motors do not transport the microtubules but instead enable the microtubules to participate in events such as growth cone turning or axonal retraction. In order for microtubules to be mobile, they must be cut into short pieces by enzymes called microtubule-severing proteins.  Thus, the behavior and configuration of the microtubules and the roles they perform are dependent upon the forces generated by molecular motor proteins as well as the activity of microtubule-severing proteins that determine the consequences of these motor-driven forces on the microtubules.

Peter Baas laboratory research image, Retracting Axon / Elongating Axon / Navigating Growth Cone

There are two major projects currently underway in the Baas Laboratory. The first is a direct continuation of the studies on the cellular and molecular mechanisms that orchestrate microtubules during development.  These studies include live-cell imaging of microtubules in neurons, together with manipulations of the relevant molecular motor proteins such as cytoplasmic dynein and kinesin-5.  These studies also include a strong focus on the microtubule-severing proteins, namely katanin and spastin.  The studies are aimed at understanding how axons grow, how dendrites are differentiated, how axonal branches are formed, and how growth cones navigate to find their targets. 

Shown in this figure is a recent experiment in which the distribution of kinesin-5 was determined during the turning of a growth cone, leading to a mechanistic model whereby kinesin-5 cooperates with other motors to regulate the polarized distribution of microtubules that is essential for a growth cone to make a turn.

Distribution of kinesin-5 determined during turning of growth cone

The second major project focuses on how these microtubule-based mechanisms go awry during neurodegenerative diseases as well as nerve injury, and how the growing body of knowledge about neuronal microtubules can be used to develop new therapeutic strategies for treating injured or diseased axons. For example, mutations of the spastin gene are the most common cause of hereditary spastic paraplegia, and the Baas Laboratory is actively seeking to understand how the mutant forms of spastin cause the corticospinal tracts to degenerate. Other studies in the laboratory include testing the hypothesis that axons may degenerate during Alzheimer’s disease because of too much microtubule-severing when the tau protein dissociates from the microtubules. In addition, there are ongoing projects on how manipulation of certain molecular motors and severing proteins might provide avenues for clinical strategies to augment regeneration of damaged nerves after injury.

Possible Katanin/Spastin Gene Therapy for Spinal Cord Repair


Selected Publications

"Tau: It's Not What You Think"
Baas PW, Qiang L
Trends Cell Biol. 2019 Mar 28. pii: S0962-8924(19)30038-8. doi: 10.1016/j.tcb.2019.02.007. [Epub ahead of print] Review. PMID: 30929793

"Mitotic Motor KIFC1 is an organizer of microtubules in the axon"
Muralidharan H, Baas PW
J Neurosci. 2019 Feb 25. pii: 3099-18. doi: 10.1523/JNEUROSCI.3099-18.2019. [Epub ahead of print] PMID: 30804089

"Knockdown of Fidgetin Improves Regeneration of Injured Axons by a Microtubule-Based Mechanism"
Matamoros AJ, Tom VJ, Wu D, Rao Y, Sharp DJ, Baas PW
J Neurosci. 2019 Mar 13;39(11):2011-2024. doi: 10.1523/JNEUROSCI.1888-18.2018. Epub 2019 Jan 15. PMID: 30647150

"Hereditary spastic paraplegia: gain-of-function mechanisms revealed by new transgenic mouse"
Qiang L, Piermarini E, Muralidharan H, Yu W, Leo L, Hennessy LE, Fernandes S, Connors T, Yates PL, Swift M, Zholudeva LV, Lane MA, Morfini G, Alexander GM, Heiman-Patterson TD, Baas PW
Hum Mol Genet. 2019 Apr 1;28(7):1136-1152. doi: 10.1093/hmg/ddy419. PMID: 30520996

"Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9-mediated kif15 mutations accelerate axonal outgrowth during neuronal development and regeneration in zebrafish"
Dong Z, Wu S, Zhu C, Wang X, Li Y, Chen X, Liu D, Qiang L, Baas PW, Liu M
Traffic. 2019 Jan;20(1):71-81. doi: 10.1111/tra.12621. Epub 2018 Nov 29. PMID: 30411440

"Tau Does Not Stabilize Axonal Microtubules but Rather Enables Them to Have Long Labile Domains"
Qiang L, Sun X, Austin TO, Muralidharan H, Jean DC, Liu M, Yu W, Baas PW
Curr Biol. 2018 Jul 9;28(13):2181-2189.e4. doi: 10.1016/j.cub.2018.05.045. Epub 2018 Jun 28. PMID: 30008334

"Polarity Sorting of Microtubules in the Axon"
Rao AN, Baas PW
Trends Neurosci. 2018 Feb;41(2):77-88. doi: 10.1016/j.tins.2017.11.002. Epub 2017 Nov 30. Review. PMID: 29198454

"Polarity sorting of axonal microtubules: a computational study" [PDF]
Craig EM, Yeung HT, Rao AN, and Baas PW
Molecular Biology of the Cell 28(23):3271-3285. doi:10.1091/mbc.E17-06-0380 (November 2017)

"Nanoparticle Delivery of Fidgetin siRNA as a Microtubule-based Therapy to Augment Nerve Regeneration" [PDF]
Austin TO, Matamoros AJ, Friedman JM, Friedman AJ, Nacharaju P, Yu W, Sharp DJ & Baas PW
Scientific Reports, 7:9675, DOI:10.1038/s41598-017-10250-z (August 2017)

"Cytoplasmic Dynein Transports Axonal Microtubules in a Polarity-Sorting Manner" [PDF]
Rao AN, Patil A, Black MM, Craig EM, Myers KA, Yeung HT & Baas PW
Cell Reports, 19, 2210–2219 (June 2017)

"Pharmacologically increasing microtubule acetylation corrects stress-exacerbated effects of organophosphates on neurons"
Rao AN, Patil A, Brodnik ZD, Qiang L, España RA, Sullivan KA, Black MM, Baas PW
Traffic, 18(7):433-441. doi: 10.1111/tra.12489. Epub 2017 May 25 (July 2017)

"Reprogramming cells from Gulf War veterans into neurons to study Gulf War illness"
Qiang L, Rao AN, Mostoslavsky G, James MF, Comfort N, Sullivan K, Baas PW
Neurology, 88(20):1968-1975. doi: 10.1212/WNL.0000000000003938 (May 16, 2017)

"Truncating mutations of SPAST associated with hereditary spastic paraplegia indicate greater accumulation and toxicity of the M1 isoform of spastin" [PDF]
Solowska JM, Rao AN, and Baas PW
Molecular Biology of the Cell 28(13):1728-1737. doi:10.1091/mbc.E17-01-0047 (May 2017)

"Mutant spastin proteins promote deficits in axonal transport through an isoform-specific mechanism involving casein kinase 2 activation" [PDF]
Lanfranco Leo, Carina Weissmann, Matthew Burns, Minsu Kang, Yuyu Song, Liang Qiang, Scott T. Brady, Peter W. Baas, and Gerardo Morfini
Human Molecular Genetics, doi: 10.1093/hmg/ddx125 (epub April 7, 2017)

"Microtubules in Health and Degenerative Disease of the Nervous System" [PDF]
Matamoros AJ, Baas PW
Brain Res Bull. 126(Pt 3):217-225. doi: 10.1016/j.brainresbull.2016.06.016. Epub 2016 Jun 27. (September 2016)

"Stability Properties of Neuronal Microtubules" [PDF]
Baas PW, Rao AN, Matamoros AJ, Leo L
Cytoskeleton, 73:442–460 (September 2016)

"Microtubules: Organization and Function in Neurons Introductory Article"
P.W. Baas, K.A. Myers, L. Qiang, V.C. Nadar
In: Reference Module in Biomedical Sciences, pub: Elsevier B.V. (2014)

"Mitotic motors coregulate microtubule patterns in axons and dendrites"
Lin S, Liu M, Mozgova OI, Yu W, Baas PW
J Neurosci. 32(40):14033-49 (Oct 3, 2012).

"Septin-driven coordination of actin and microtubule remodeling regulates the collateral branching of axons"
Hu J, Bai X, Bowen JR, Dolat L, Korobova F, Yu W, Baas PW, Svitkina T, Gallo G, Spiliotis ET.
Curr Biol. 22(12):1109-15 (Jun 19, 2012).

M"icrotubule redistribution in growth cones elicited by focal inactivation of kinesin-5"
Nadar VC, Lin S, Baas PW
J Neurosci. 32(17):5783-94 (Apr 25, 2012).

"Partial interruption of axonal transport due to microtubule breakage accounts for the formation of periodic varicosities after traumatic axonal injury"
Tang-Schomer MD, Johnson VE, Baas PW, Stewart W, Smith DH
Exp Neurol. 233(1):364-72 (Jan 2012).

"Hooks and Comets: The Story of Microtubule Polarity Orientation in the Neuron"
Baas PW, Lin S
Developmental Neurobiology; 71(6):403-418 (June 21, 2011).

"Kinesin-5, a mitotic microtubule-associated motor protein, modulates neuronal migration"
Falnikar A, Tole S, and Baas PW
Molecular Biology of the Cell; 22:1561-1574 (May 1, 2011).

"Inhibition of kinesin-5, a microtubule-based motor protein, as a strategy for enhancing regeneration of adult axons"
Lin S, Liu M, Son YJ, Himes BT, Snow DM, Yu W, Baas PW
Traffic; 12:269-286 (Jan 17, 2011).

"Strategies for diminishing katanin-based loss of microtubules in tauopathic neurodegenerative diseases"
Sudo H, Baas PW
Human Molecular Genetics; 20(4):763-778 (Feb 15, 2011).

"Kinesin-12, a mitotic microtubule-associated motor protein, impacts axonal growth, navigation, and branching"
Liu M, Nadar VC, Kozielski F, Kozlowska M, Yu W, Baas PW
Journal of Neuroscience; 30(44):14896-906 (Nov 3, 2010).

"Evaluation of loss of function as an explanation for SPG4-based hereditary spastic paraplegia"
Solowska JM, Garbern JY, Baas PW
Human Molecular Genetics;19(14):2767-2779 (Jul 15, 2010).

"Acetylation of microtubules influences their sensitivity to severing by katanin in neurons and fibroblasts"
Sudo H and Baas PW
Journal of Neuroscience; 30(21):7215–7226 (May 26, 2010).

"Mechanical breaking of microtubules in axons during dynamic stretch injury underlies delayed elasticity, microtubule disassembly, and axon degeneration"
Tang-Schomer MD, Patel AR, Baas PW, and Smith DH
FASEB Journal; (5):1401-1410 (May 24 2010).

"Basic Fibroblast Growth Factor Elicits Formation of Interstitial Axonal Branches via Enhanced Severing of Microtubules"
Qiang L, Yu W, Liu M, Solowska JM, and Baas PW
Molecular Biology of the Cell; 21(2):334 –344 (Jan 15, 2010).

"Kinesin-5 is Essential for Growth-Cone Turning"
Nadar VC, Ketschek A, Myers KA, Gallo G, and Baas PW
Current Biology; 18(24):1972-1977 (Dec 23, 2008).

"The Microtubule-severing Proteins Spastin and Katanin Participate Differently in the Formation of Axonal Branches"
Yu W, Qiang L, Solowska JM, Karabay A, Korulu S, and Baas PW
Molecular Biology of the Cell;19(4):1485-1498 (Apr 2008).

Contact Information

Research Office

Department of Neurobiology & Anatomy
2900 W. Queen Lane
Philadelphia, PA 19129
Phone: 215.991.8298
Fax: 215.843.9082