microvilli

Human embryo at day four | Image Editor


Scanning electron micrograph of a human embryo at day 4. The protein coat surrounding the egg (zona pellucida, gold) has been slit to expose the embryonic cells inside (red). These cells go on to form the embryo and can be harvested and cultured to give rise to embryonic stem (ES) cells. Microvilli are visible on the surface of the embryonic cells (blastomeres) and numerous sperm (blue) are still visible on the outside of the zona pellucida.

Made with Flickr

HKUST scientists reveal similarities between gut microvilli and inner ear hair cell

Brush border microvilli are microscopic cellular membrane protrusions that increase the surface area of cells and carry out a wide variety of functions, including absorption, secretion and cellular adhesion. Stereocilia, on the other hand, are mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. The two structures are located in separate parts of the human body and perform vastly different functions, despite the very-similar looks and features they have.

The similarities between the two, in fact, are far more than just looks. Mechanistically, the two resembles one another just as closely.

HKUST structural biologist Mingjie Zhang and his team have found that the microvilli and the stereocilia tip-link complexes, despite only having Harmonin in common, are formed via strikingly similar interaction modes. Their findings were published in the January 25, 2016 issue of the journal Developmental Cell.

Caption: (A) The top panel summarizes the detailed protein interaction network governing the assembly of the inter-microvillar tip-link. Except for the extracellular cadherin repeat-mediated hetero-dimerization interaction between CDHR2 and CDHR5 identified recently by Tyska’s group (Crawley et al., 2014b), the rest of the interactions marked by two-way arrows have been characterized quantitatively in this study. The bottom panel is a cartoon summary of the protein interaction network in microvilli. (B) The protein interaction network governing the inner ear stereocilia tip-link complex (also known as the USH1 complex) assembly. The figure is adapted from an earlier review by Pan and Zhang (2012). The bottom panel is a cartoon summary of the protein interaction network in stereocilia adapted from an earlier review by Lu et al. (2014).Credit: HKUST Division of Life Science

Microvilli

Microvilli are microscopic cellular membrane protrusions that increase the surface area of cells, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction. These finger-like projections from the small intestine are also home to huge numbers of microbes.

Image courtesy of Azusa Hotta et al., Journal of Cell Biology

Similarities Between Gut Microvilli and Inner Ear Hair Cell Revealed

Brush border microvilli are microscopic cellular membrane protrusions that increase the surface area of cells and carry out a wide variety of functions, including absorption, secretion and cellular adhesion. Stereocilia, on the other hand, are mechanosensing organelles of hair cells, which respond to fluid motion in numerous types of animals for various functions, including hearing and balance. The two structures are located in separate parts of the human body and perform vastly different functions, despite the very-similar looks and features they have.

The research is in Developmental Cell. (full access paywall)

Structure of the Small Intestine

-Large folds of mucosa maximizes the surface area

-Villi are finger-like projections lined with absorptive cells

-Microvilli form a brush border on the surface of the villi

            *Trap nutrients

            * Most of the digestive enzymes produced by the SI are found here

-Crypts of Leiberkühn

            *Tubular pits located between the villi

            *Houses stem cells to replace the epithelial cells of the villi

            * Lined with young endocrine cells

                        +Panath cells: defense against microbes in the SI

                        +Goblet cells: Secrete mucosa

                        +Enterochromaffin cells: Endocrine functions

            *The young cells migrate toward the tip of the villi and become absorptive epithelial cells

            *Cell turnover is 3-5 days