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Jo Ann Cameron

Professor Emeritus of Cell & Developmental Biology

Research Interests

Development, Pattern Formation

Research Description

Cellular and molecular mechanisms that control amphibian limb regeneration

We are conducting studies that will provide insight into why most adult vertebrates, including humans, lose the ability to regenerate their limbs. The same principles that apply to developing systems often hold true for regenerating systems. Our laboratory has a longstanding interest in how vertebrate limb pattern is established during development and regeneration. For instance, the developmental potential of salamander limb buds (newly developing limbs) and regeneration blastemas (regenerating limbs) is changed predictably by application of retinoic acid (Ludolph et al., 1993). Successful vertebrate limb regeneration is accomplished by formation, continued growth, patterning, and differentiation of a regeneration blastema at the cut surface of a limb stump. Mature tissues adjacent to the amputation surface lose their extracellular matrix and cells reenter the cell cycle in preparation for stump repair and regeneration of the lost parts. At the cellular level a regeneration blastema resembles the original embryonic limb bud that gives rise to the mature limb.

Presently we are examining initial cellular and molecular events in the stump following partial hindlimb amputation in premetamorphic and metamorphic Xenopus laevis (African Clawed Frog). Premetamorphic tadpoles can regenerate hindlimb parts, while the ability to regenerate declines as the tadpole undergoes metamorphosis. Tadpole hindlimb regeneration provides a natural loss-of-function system that resembles the typical loss of ability to regenerate in vertebrates. We find that within several premetamorphic stages, the ability to replace lost limb parts is most pronounced at the more distal levels (toe tips) compared to the more proximal levels (Nye et al., 1997; Zimmerman et al., 1999). In addition, we are examining the skeletal elements at the amputation sites to determine whether they are cartilaginous or ossified. Amputation through bone results in less successful regeneration than amputation through cartilage (Nye et al., 1998). This observation may explain, in part, why older limbs do not regenerate as well as younger ones. It is possible that bone tissue cannot contribute to blastema formation as effectively as cartilage. We are studying cellular features of blastemas at the developmental stages and amputation levels where there is predictably “good regeneration” and where there is predictably “poor” regeneration. Blastemas with cellular characteristics most closely resembling limb buds are more likely to regenerate successfully (Wolfe et al., 2000). One hypothesis we are investigating is that the cellular features of “good” and “poor” blastemas can be used to predict whether a particular blastema will regenerate more or less completely.

Knowing the cellular features of blastemas that give rise to more complete regenerates compared to those that will not regenerate gives us insight into possible changes in the expression patterns of certain genes in tadpole hindlimb cells following amputation. From our work and the work of other investigators we know that many of the same genes important during embryonic limb development are expressed again during limb regeneration. Patterning factors like sonic hedgehog, Hox genes and Msx, and growth factors like Fgfs are expressed during limb regeneration. Expression patterns of these genes provide spatially arranged cell signaling centers within limb buds at each developmental stage and similar centers within regeneration blastemas during regeneration. Particular genes may not be expressed or their expression pattern may change when regeneration fails. A second hypothesis we are investigating is that the loss of ability to regenerate is correlated with the change in ability to express developmentally-regulated genes in hindlimb cells following amputation.

Our understanding of the cellular and molecular mechanisms associated with the loss of regenerative ability during frog metamorphosis will form a basis for future studies directed toward extending the ability of Xenopus tadpoles and frogs to replace limb parts.


B.S., University of Wisconsin (Zoology and Secondary Education) 
Ph.D., University of Wisconsin (Anatomy) 
Postdoc., University of Virginia-Charlottesville

Highlighted Publications

Rao N, Song F, Jhamb D, Wang M, Milner DJ, Price NM, Belecky-Adams TL, Palakai MJ, Cameron JA, Li B, Chen X, Stocum DL. (2014) Proteomic analysis of fibroblastema formation in regenerating hind limbs of Xenopus laevis froglets and comparison to axolotl. BMC Developmental Biology, 14:32. PMID: 25063185

Milner DJ, Cameron JA. (2013) Muscle repair and regeneration: stem cells, scaffolds, and the contributions of skeletal muscle to amphibian limb regeneration. In: DL Stocum and E Heber-Katz (eds) Current Topics in Microbiology and Immunology, Vol. 367, Springer-Verlag, Heidelberg, pp. 133-159. Review PMID: 23224711

Cameron JA, Milner DJ, Lee JS, Cheng J, Fang NX, Jasiuk IM. (2013) Employing the biology of successful fracture repair to heal critical size bone defects. In: DL Stocum and E Heber-Katz (eds) Current Topics in Microbiology and Immunology, Vol. 367, Springer-Verlag, Heidelberg, pp. 113-132. Review PMID: 23239235

Feng L, Milner DJ, Xia C, Nye HLD, Redwood P, Cameron JA, Stocum DL, Fang NX, Jasiuk IM. (2011) Xenopus laevis as a Novel Model to Study Long Bone Critical Size Defect Repair by Growth Factor Mediated Regeneration. Tissue Engineering Part A,17:691-701. PMID: 20929280

Jhamb D, Rao N, Milner DJ, Song F, Cameron JA, Stocum DL, Palakal MJ. (2011) Network based transcription factor analysis of regenerating axolotl limbs. BMC Bioinformatics, 12:80. PMID: 21418574 

Stocum DL, Cameron JA. (2011) Looking Proximally and Distally: 100 Years of Limb Regeneration and Beyond. Developmental Dynamics, 240:943-968. PMID: 21290477

Rao N, Jhamb D, Milner DJ, Li B, Song F, Wang M, Voss SR, Palakal M, King M, Saranjami B, Nye HLD, Cameron JA, Stocum DL. (2009) Proteomic Analysis of Blastema Formation in Regenerating Axolotl Limbs. BMC Biology, 7:83. PMID: 19948009

Nye, HLD, Cameron JA. (2005) Strategies to Reduce Variation in Xenopus laevisRegeneration Studies. Developmental Dynamics 234:151-158. PMID: 16032711

Wolfe AD, Crimmins G, Cameron JA, Henry JJ. (2004) Early Regeneration Genes: Building a Molecular Profile for Shared Expression in Cornea-Lens Transdifferentiation and Hind Limb Regeneration in Xenopus laevis. Developmental Dynamics 230: 615-629. PMID: 15254896

Holly L.D. Nye, Jo Ann Cameron, Ellen A.G. Chernoff, David L. Stocum (2003) Extending the table of normal development of the axolotl: limb development. Developmental Dynamics 226:555-560. PMID: 12619140

Chernoff, Ellen A.G., David L. Stocum, Holly L.D. Nye, Jo Ann Cameron (2003) Urodele spinal cord regeneration and related processes. Developmental Dynamics 226:295-307. PMID: 12557207

Nye, Holly L.D., Jo Ann Cameron, Ellen A.G. Chernoff, David L. Stocum (2003) Regeneration of the urodele limb: a review. Developmental Dynamics 226:280-294. PMID: 12557206 

Wolfe, Adam D., Holly L.D. Nye, and Jo Ann Cameron. (2000) Extent of ossification at the amputation plane is correlated with the decline of blastema formation and regeneration in Xenopus laevis hindlimbs. Developmental Dynamics 218:681-697. PMID: 10906786 

Ludolph, David C., Jo Ann Cameron, and David L. Stocum. (1994) Test of a Model for the Effects of Retinoic Acid on Urodele Limb Regeneration. Developmental Dynamics, 198:77-85. PMID: 8305708

Ludolph, David C., Jo Ann Cameron, Anthony Neff, and David L. Stocum. (1993) Cloning and Tissue-Specific Expression of the Axolotl Cellular Retinoic Acid Binding Protein. Development Growth and Differentiation, 35:341-347. DOI: 10.1111/j.1440-169X.1993.00341.X

Ludolph, David C., Jo Ann Cameron, and David L. Stocum. (1993) Asymmetric Effects of Retinoic Acid on Pattern Formation in the Transverse Axes of Regenerating Axolotl Limbs: Test of An Hypothesis. In Limb Development and Regeneration Wiley-Liss, Inc., pp. 739-747. PMID: 8115389

Christ, Connie B., Richard A. Boileau, Mary H. Slaughter, Rachel J. Stillman, and Jo Ann Cameron. (1993) The effect of test protocol instructions on the measurement of muscle function in adult women. J. Orthopaedic and Sports Physical Therapy, 18:502-510. doi: 10.2519/jospt.1993.18.3.502

Monkemeyer, Jon, David Ludolph, Jo Ann Cameron, and David Stocum. (1992) Dose-Response of Anteroposterior Positional Identity to Retinoic Acid in Regenerating Axolotl Limbs. Developmental Dynamics, 193:286-294. PMID: 1600247

Christ, Connie B., Richard A. Boileau, Mary H. Slaughter, Rachel J. Stillman, Jo Ann Cameron, and B. H. Massey. (1992) Maximal Voluntary Isometric Force Production Characteristics of Six Muscle Groups in Women Aged 25 to 74 Years. American Journal of Human Biology, 4:537-545. DOI: 10.1002/ajhb.1310040413

Ludolph, David C., Jo Ann Cameron, and David L. Stocum. (1990) The effect of retinoic acid on positional memory in the dorsoventral axis of regenerating axolotl limbs. Developmental Biology, 140:41-52. PMID: 2358123

Hinterberger, Timothy and Jo Ann Cameron. (1990) Myoblasts and connective tissue cells in regenerating amphibian limbs. Ontogenez, 21:341-357. (Also in Russian) PMID: 2234787

McPhoil, T., Cameron JA, Adrian, MJ. (1987) Anatomical characteristics of the talus in relation to forefoot dformities. J Am Podiatr Med Assoc. 77:77-81. PMID: 3559940

Cameron, Jo Ann, Allen Hilgers, and Timothy Hinterberger. (1986) Evidence that reserve cells are a source of regenerated adult newt muscle in vitro. Nature, 321:607-610. doi: 10.1038/321607.a0 

Cameron, Jo Ann and Timothy J. Hinterberger. (1984) Regional differences in the distribution of myogenic and chondrogenic cells in axolotl limb blastemas. J. Exp. Zool., 232:269-276. doi: 10.1002/jez.1402320214

Schrag, Joan A. and Jo Ann Cameron. (1983) Regeneration of adult newt skeletal muscle in vitro. J. Embryol. Exp. Morph., 77:255-271. PMID: 6655433

Hinterberger, Timothy J. and Jo Ann Cameron. (1983) Muscle and cartilage differentiation in axolotl limb regeneration blastema cultures. J. Exp. Zool., 226:399-407. PMID: 6886662

Chew, Keith E. and Jo Ann Cameron. (1983) Increase in mitotic activity of regenerating axolotl limbs by growth factor impregnated implants. J. Exp. Zool., 226:325-329. doi: 10.1002/jez.1402260220

Cameron, Jo Ann. (1983) Regeneration of skeletal muscle in Notophthalamus viridescens. In The Proceedings of the Third International Conference on Limb Development and Regeneration. New York, Alan R. Liss, Inc., pp. 491-500.

Fallon, John F. and Jo Ann Cameron. (1977) Interdigital cell death during limb development of the turtle and lizard with an interpretation of evolutionary significance. J. Embryol. Exp. Morph., 40:285-289. PMID: 915430 

Cameron, Jo Ann and John F. Fallon. (1977) The absence of cell death during development of free digits in Amphibians. Developmental Biology, 55:331-338. PMID: 838123 

Cameron, Jo Ann and John F. Fallon. (1977) Evidence for polarizing zone in the limb buds of Xenopus laevis. Developmental Biology, 55:320-330. PMID: 838122 

Recent Publications

Click here for Dr. Cameron's complete publications list.