Mary K. Montgomery

Embryonic Development of the Light Organ of the Sepiolid Squid Euprymna scolopes Berry

The sepiolid squid Euprymna scolopes maintains luminous bacterial symbionts of the species Vibrio fischeri in a bilobed light organ partially embedded in the ventral surface of the ink sac. Anatomical and ultrastructural observations of the light organ during embryogenesis indicate that the organ begins development as a paired proliferation of the mesoderm of the hindgut-ink sac complex. Three-dimensional reconstruction of the incipient light organ of a newly hatched juvenile revealed the presence of three pairs of sacculate crypts, each crypt joined to a pore on the surface of the light organ by a ciliated duct. The crypts, which become populated with bacterial symbionts within hours after the juvenile hatches, appear to result from sequential paired invaginations of the surface epithelium of the hindgut-ink sac complex during embryogenesis. A pair of anterior and a pair of posterior ciliated epithelial appendages, which may facilitate infection of the incipient light organ with symbiotic bacteria, develop by extension and growth of the surface epithelium. The ink sac and reflector develop dorsal to the crypts and together function to direct luminescence ventrally. These two accessory tissues are present at the time of hatching, although changes in their overall structure accompany growth and maturation of the light organ. A third accessory tissue, the muscle-derived lens, appears during post-hatch maturation of the light organ.

RNA interference: unraveling a mystery.

Andrew Fire and Craig Mello have won the Nobel Prize in Medicine or Physiology for their discovery of RNA interference. Mary K. Montgomery, then a postdoc in the Fire laboratory, participated in some of the key experiments.

The Use of Double-Stranded RNA to Knock Down Specific Gene Activity

In many eukaryotes, the introduction of double-stranded RNA (dsRNA) into cells triggers the degradation of cognate mRNAs through a posttranscriptional gene silencing mechanism. This phenomenon has been called RNA interference or RNAi. Several methods for delivering dsRNA into the model organism C. elegans are described; these methods include (1) microinjecting dsRNA synthesized in vitro into the body cavity of the worm, (2) soaking worms in a solution of dsRNA, (3) feeding worms dsRNA-expressing bacteria, and (4) engineering transgenic worm strains to express dsRNA in vivo. Variations of these methods may be used to perform RNAi in other species as well. The choice of which delivery method to use, along with other options (region to target, length of dsRNA) are also discussed.