Ronald J. Konopka

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Ronald J. Konopka (1947-2015) was an American geneticist who studied chronobiology. [1] He made his most notable contribution to the field while working with Drosophila in the lab of Seymour Benzer at the California Institute of Technology. During this work, Konopka discovered the period (per) gene, which controls the period of circadian rhythms. [2] [3]

Contents

Academic career

Ron Konopka received his Ph.D. in Biology from the California Institute of Technology in 1972. In 1975, following his discovery of the period mutants, Konopka was awarded a faculty position at the California Institute of Technology. While there, Konopka's colleagues were critical of his reluctance to publish his work on the period gene, and Konopka was denied tenure. After his stay at Caltech, Konopka accepted a position at Clarkson University but was again denied tenure and subsequently exited the field of science. [4] Konopka's career, interwoven with the work of his mentor, Seymour Benzer, and the other scientists working in Benzer's lab is narrated in Time, Love, Memory by Jonathan Weiner.

Konopka's discovery and genetic analysis of period and several other circadian rhythm mutations became the basis of the research done by Drs. Jeffrey C. Hall, Michael Rosbash, and Michael W. Young, who were awarded the 2017 Nobel Prize in Physiology or Medicine.

Research

Period mutants

Discovery of Period

As a graduate student in Seymour Benzer's lab, Konopka sought to use Benzer's method of behavioral genetics to unravel the mysteries of the "master clock" that existed in every organism. [5] He used ethyl methanesulfonate (EMS) to induce point mutations in the Drosophila melanogaster genome, and eventually isolated three mutants with abnormal rhythms in eclosion. He mapped the mutations to the same location on the far left of the X chromosome, less than 1 centimorgan away from the white gene locus. These mutations were alternative alleles of a gene that Konopka subsequently named period. [6] While wild type flies have a circadian period around 24 hours, Konopka found the per01 mutant was arrhythmic, the perS mutant had a period of 19 hours, and the perL had a period of 29 hours.

Neurobiology of per mutants

In 1979 and a 1980, Konopka and Dominic Orr tested whether mutations in per mutations affected the period of the entire circadian cycle or just a portion of it. By comparing the light responses of perS eclosion rhythm to that of wild type flies, Konopka and Orr found that light pulses reset the mutant clock to a greater extent than the wild type clock (about 10 hours for perS compared to 3 hours for wild type flies). They also observed that the while duration of the light-sensitive part of the day (subjective night) was found to be similar between perS and wild type flies, the duration of the light-insensitive part of the cycle (subjective day) was 5 hours shorter in mutant flies than in wild type flies. They concluded that differences in period length between mutant and wild type flies could be accounted for by a shortening of the subjective day, or the active part of the circadian cycle, in perS mutants. From this, Konopka concluded that separate molecular processes correspond to the subjective night and subjective day and that the perS allele acts by shortening the subjective day while leaving the subjective night unchanged. Based on these findings, Konopka and Orr constructed a model for the action of the per gene. The oscillation is interpreted in terms of a membrane gradient that is established during the subjective day and dissipates during the subjective night. The model predicts that the per gene product is active during the subjective day and functions like a pump to establish the gradient. Once a high threshold is reached, the pump shuts off and light-sensitive channels open to dissipate the gradient. A light pulse during the subjective night closes the channels and starts the pump; the value of the gradient when the channels close is the same as the value when the pump starts, and thus a reset in the cycle is produced and an oscillation results. [7] This model has been replaced with a transcription translation negative feedback model involving timeless, clock, and cycle. [8]

Also in 1980, Konopka and Steven Wells reported an abnormality in the morphology of a neurosecretory cell group associated with the arrhythmic per01 mutation and with 2 arrhythmic mutants of another fly strain, Drosophila pseudoobscura . This cell group normally consists of four clustered cells in either side of the brain, roughly halfway between the top and bottom edge, in the posterior area of the brain. Cells in this cluster are occasionally located abnormally near the top edge, rather than the middle, of the brain at a rate of about 17% of cells in wild-type D. melanogaster. The per01 mutation significantly increases the percentage of abnormally located cells to about 40%. In two aperiodic strains of D. pseudoobscura, the percentages of abnormally located cells are likewise significantly increased over those in the wild type. Konopka inferred from the results that neurosecretory cells may be part of the Drosophila circadian system and that per gene product may influence the development of these cells. [9]

Pacemaker signalling

In 1979 Konopka worked with Alfred Handler to discover the nature behind pacemaker signalling by transplanting brains of donor flies into abdomens of arrhythmic host flies. They found that circadian rhythms in host flies were restored with the period of the donor; for example, short period (perS) adult brains implanted into the abdomens of arrhythmic (per01) hosts could confer a short period rhythm on the activity of some hosts for at least 4 cycles. [10] Since the transplanted brains were unable to create new neuronal connections to locomotor activity centers, Konopka and Handler concluded that pacemaker signalling for locomotion must be humoral and not neuronal. [10]

Reciprocal behavior of per mutants

While at Clarkson College, Konopka continued his work with Orr and also collaborated with chronobiologist Colin Pittendrigh. During the collaboration, Konopka worked to understand behaviors of Drosophilaper mutants beyond their abnormal period lengths. Konopka was primarily interested in how these mutants behaved in constant light or constant darkness and whether they conformed to the rules established by chronobiologist Jurgen Aschoff. In addition, Konopka also observed behavior of the flies under varying light intensities and over a range of temperatures. Konopka found that the perS and perL flies showed reciprocal behaviors under the experimental conditions. [11] For example, perS period shortened, while perL period lengthened in response to decreasing temperature. [11] Konopka hypothesized that these reciprocal behaviors were a manifestation of two coupled oscillators, a model proposed in 1976 by Pittendrigh and Daan. [12]

Other circadian mutants

Clock mutants

In 1990, Konopka collaborated with Mitchell S. Dushay and Jeffery C. Hall to further investigate the effects of the clock gene in D. melanogaster. Konopka had noted in 1987 that the Clock (Clk) mutant, induced via chemical mutation, was a semidominant mutation that shortened the rhythm of locomotor activity in flies by around 1.5hr. [7] Dushay, Konopka and Hall noted that Clk mutants had phase response curve that was shortened from 24hr to 22.5hr, and that the short period was also observable in the eclosion rhythm of the mutant flies. [13] Clk was mapped close enough to the per01 mutation such that it could be considered a per allele, but due to the presence normal courtship song rhythms in Clk males and the lack of coverage of its effects via duplications, Dushay and Konopka determined that Clock was a novel circadian mutation. [13]

Andante mutants

By working with Randall F. Smith and Dominic Orr of Caltech, Konopka discovered a new circadian mutant, named Andante, in 1990. [14] In contrast to Clock, Andante lengthens the period of eclosion, and locomotor activity by 1.5–2 hours, and was also shown to lengthen the periods of other circadian mutants. [14] Andante is a semi-dominant mutation, temperature compensated, and unaffected by the sine oculis mutation, which eliminates the outer visual system of flies. It was mapped to the 10E1-2 to 10F1 region of the D. melanogaster X chromosome, close to the miniature-dusky locus. [14]

Related Research Articles

Circadian rhythm Natural internal process that regulates the sleep-wake cycle

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Seymour Benzer

Seymour Benzer was an American physicist, molecular biologist and behavioral geneticist. His career began during the molecular biology revolution of the 1950s, and he eventually rose to prominence in the fields of molecular and behavioral genetics. He led a productive genetics research lab both at Purdue University and as the James G. Boswell Professor of Neuroscience, Emeritus, at the California Institute of Technology.

CLOCK

CLOCK or Clock is a gene encoding a basic helix-loop-helix-PAS transcription factor that is believed to affect both the persistence and period of circadian rhythms.

Timeless (tim) is a gene in multiple species but is most notable for its role in Drosophila for encoding TIM, an essential protein that regulates circadian rhythm. Timeless mRNA and protein oscillate rhythmically with time as part of a transcription-translation negative feedback loop involving the period (per) gene and its protein.

Period (per) is a gene located on the X chromosome of Drosophila melanogaster. Oscillations in levels of both per transcript and its corresponding protein PER have a period of approximately 24 hours and together play a central role in the molecular mechanism of the Drosophila biological clock driving circadian rhythms in eclosion and locomotor activity. Mutations in the per gene can shorten (perS), lengthen (perL), and even abolish (per0) the period of the circadian rhythm.

PER1

The PER1 gene encodes the period circadian protein homolog 1 protein in humans.

In molecular biology, an oscillating gene is a gene that is expressed in a rhythmic pattern or in periodic cycles. Oscillating genes are usually circadian and can be identified by periodic changes in the state of an organism. Circadian rhythms, controlled by oscillating genes, have a period of approximately 24 hours. For example, plant leaves opening and closing at different times of the day or the sleep-wake schedule of animals can all include circadian rhythms. Other periods are also possible, such as 29.5 days resulting from circalunar rhythms or 12.4 hours resulting from circatidal rhythms. Oscillating genes include both core clock component genes and output genes. A core clock component gene is a gene necessary for to the pacemaker. However, an output oscillating gene, such as the AVP gene, is rhythmic but not necessary to the pacemaker.

Colin Stephenson Pittendrigh was a British-born biologist who spent most of his adult life in the United States. Pittendrigh is regarded as the "father of the biological clock," and founded the modern field of chronobiology alongside Jürgen Aschoff and Erwin Bünning. He is known for his careful descriptions of the properties of the circadian clock in Drosophila and other species, and providing the first formal models of how circadian rhythms entrain (synchronize) to local light-dark cycles.

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<i>Cycle</i> (gene)

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Michael Rosbash

Michael Morris Rosbash is an American geneticist and chronobiologist. Rosbash is a professor and researcher at Brandeis University and investigator at the Howard Hughes Medical Institute. Rosbash's research group cloned the Drosophila period gene in 1984 and proposed the Transcription Translation Negative Feedback Loop for circadian clocks in 1990. In 1998, they discovered the cycle gene, clock gene, and cryptochrome photoreceptor in Drosophila through the use of forward genetics, by first identifying the phenotype of a mutant and then determining the genetics behind the mutation. Rosbash was elected to the National Academy of Sciences in 2003. Along with Michael W. Young and Jeffrey C. Hall, he was awarded the 2017 Nobel Prize in Physiology or Medicine "for their discoveries of molecular mechanisms controlling the circadian rhythm".

Jeffrey C. Hall

Jeffrey Connor Hall is an American geneticist and chronobiologist. Hall is Professor Emeritus of Biology at Brandeis University and currently resides in Cambridge, Maine.

Michael W. Young

Michael Warren Young is an American biologist and geneticist. He has dedicated over three decades to research studying genetically controlled patterns of sleep and wakefulness within Drosophila melanogaster.

Jeffrey L. Price is an American researcher and author in the fields of circadian rhythms and molecular biology. His chronobiology work with Drosophila melanogaster has led to the discoveries of the circadian genes timeless (tim) and doubletime (dbt), and the doubletime regulators spaghetti (SPAG) and bride of doubletime (BDBT).

Paul Hardin is a prominent scientist in the field of chronobiology and a pioneering researcher in the understanding of circadian clocks in flies and mammals. Hardin currently serves as a distinguished professor in the biology department at Texas A&M University. He is best known for his discovery of circadian oscillations in the mRNA of the clock gene Period (per), the importance of the E-Box in per activation, the interlocked feedback loops that control rhythms in activator gene transcription, and the circadian regulation of olfaction in Drosophila melanogaster. Born in a suburb of Chicago, Matteson, Illinois, Hardin currently resides in College Station, Texas, with his wife and three children.

Vrille (vri) is a bZIP transcription factor found on chromosome 2 in Drosophila melanogaster. Vrille mRNA and protein product (VRI) oscillate predictably on a 24-hour timescale and interact with other circadian clock genes to regulate circadian rhythms in Drosophila. It is also a regulator in embryogenesis; it is expressed in multiple cell types during multiple stages in development, coordinating embryonic dorsal/ventral polarity, wing-vein differentiation, and ensuring tracheal integrity. It is also active in the embryonic gut but the precise function there is unknown. Mutations in vri alter circadian period and cause circadian arrhythmicity and developmental defects in Drosophila.

<i>Drosophila</i> circadian rhythm

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References

  1. ↑ Rosbash, Michael (April 9, 2015). "Ronald J. Konopka (1947–2015)". Cell. 161 (2): 187–188. doi: 10.1016/j.cell.2015.03.038 . PMID   26042238.
  2. ↑ Denlinger, David L.; J. M. Giebultowicz; David Stanley Saunders (2001). Insect timing: circadian rhythmicity to seasonality. Gulf Professional Publishing. p. 17. ISBN   978-0-444-50608-5 . Retrieved March 31, 2011.
  3. ↑ Greenspan, Ralph, (2003). "The 2003 Genetics Society of America Medal" Retrieved April 13, 2011.
  4. ↑ Barondes, S (2000) A Real-life Arrowsmith Finds His Sinclair Lewis Retrieved April 13, 2011.
  5. ↑ Weiner, Jonathan. "Time, Love, Memory: A Great Biologist and His Quest for the Origins of Behavior" Alfred A. Knopf, Inc, 1999
  6. ↑ Konopka, R.; Benzer, Seymour (1971). "Clock Mutants of Drosophila melanogaster". Proc. Natl. Acad. Sci. 68 (9): 2112–6. Bibcode:1971PNAS...68.2112K. doi: 10.1073/pnas.68.9.2112 . PMC   389363 . PMID   5002428.
  7. 1 2 Konopka, Ronald J (1987). "Genetics of Biological Rhythms in Drosophila". Annu. Rev. Genet. 21: 227–236. doi:10.1146/annurev.ge.21.120187.001303. PMID   3327464.
  8. ↑ Ishida N, Kaneko M, Allada R (August 1999). "Biological clocks". Proc. Natl. Acad. Sci. U.S.A. 96 (16): 8819–20. Bibcode:1999PNAS...96.8819I. doi: 10.1073/pnas.96.16.8819 . PMC   33693 . PMID   10430850.
  9. ↑ Konopka, RJ; Wells (1980). "Drosophila clock mutations affect the morphology of a brain neurosecretory cell group". Journal of Neurobiology. 11 (4): 411–415. doi:10.1002/neu.480110407. PMID   7400816.
  10. 1 2 Handler, A & Konopka, R (1979). "Transplantation of a circadian pacemaker in Drosophila". Nature. 279 (5710): 236–238. Bibcode:1979Natur.279..236H. doi:10.1038/279236a0. PMID   440433. S2CID   4369719.
  11. 1 2 Konopka RJ, Pittendrigh C, Orr D (2007). "Reciprocal behaviour associated with altered homeostasis and photosensitivity of Drosophila clock mutants". J. Neurogenet. 21 (4): 243–52. doi:10.1080/01677060701695391. PMID   18161586. S2CID   25159075.
  12. ↑ Pittendrigh CS, Daan S (1976). "A functional analysis of circadian pacemakers in nocturnal rodents V. Pacemaker structure: a clock for a seasons". J. Comp. Physiol. 106: 333–55. doi:10.1007/BF01417860. S2CID   206794951.
  13. 1 2 Dushay MS, Konopka RJ, Orr D, Greenacre ML, Kyriacou CP, Rosbash M, Hall JC (1990). "Phenotypic and genetic analysis of Clock, a new circadian rhythm mutant in Drosophila melanogaster". Genetics. 125 (3): 557–78. doi:10.1093/genetics/125.3.557. PMC   1204083 . PMID   2116357.
  14. 1 2 3 Konopka RJ, Smith RF, Orr D (1991). "Characterization of Andante, a new Drosophila clock mutant, and its interactions with other clock mutants". J. Neurogenet. 7 (2–3): 103–114. doi:10.3109/01677069109066214. PMID   2030465.
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