Date Thesis Awarded

5-2018

Access Type

Honors Thesis -- Access Restricted On-Campus Only

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Diane Shakes

Committee Members

Oliver Kerscher

Matthew Wawersik

Robert Scholnick

Abstract

Meiosis, particularly the first, reductive division, is extraordinarily complex, and as such requires extensive preparation. The extended prophase of the first meiotic division provides developing gametes the opportunity to carry out this intense preparation. When components of this developmental stage are altered, catastrophic consequences, such as failure to produce functional gametes, may result (Lee 2009, Klovstad 2008, Updike 2011). In the case of spe-6(hc49) C. elegans, lack of functional SPE-6 protein prevents sperm production; affected spermatocytes arrest in late meiotic prophase, prior to the transition into the division phase (Varkey 1993). Ultimately, this results in complete male infertility and prevents self-fertility in hermaphrodites. Although SPE-6 has been identified as an essential kinase for spermatogenesis, relatively little is understood about its actual role in sperm production. A systematic review of whether particular developmental events occur properly in the absence of SPE-6 could identify specific roles for the protein in spermatogenesis. This study included three main avenues of investigation: 1) in spermatocytes lacking functional SPE-6, what events of late meiotic prophase are relatively unaffected?; 2) can new markers provide a more precise characterization of the spe-6(hc49) arrest, originally classified as a nuclear arrest in diakinesis?; 3) in the absence of functional SPE-6, is there a defect in rachis detachment?

Here, new markers were used to systematically characterize the chromatin and cytoskeleton remodeling events leading up to the failed diakinesis in spe-6(hc49) spermatocytes. Several aspects of meiotic prophase chromatin remodeling, including entry to the karyosome substage, were shown to be relatively unaffected in spe-6(hc49) spermatocytes. In addition, several aspect of M-phase entry occur independently of spe-6(hc49). For example, use of new markers revealed evidence of nuclear envelope breakdown, suggesting a later nuclear arrest point for spe-6(hc49) spermatocytes than the originally-described diakinesis arrest. Conversely, a novel cellularization defect suggests a new role for SPE-6 in the rachis detachment process.

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