Third batch of oral reports (For December 30, 2021-January 2, 2022

Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Paula Joy Aliposa -
Number of replies: 6

Good Day Everyone!

Our group, composed of Cyrix Acar, Paula Aliposa, and Rogene Bueno of Section 3 of this course (W 10 AM - 1 PM), bring to you our report on the study of Michael Kelly and Ping Chen entitled "Development of form and function in the mammalian cochlea. 

You may access our video presentation through the following link or by clicking the image below:

For further information, the journal article by Kelly and Chen can be accessed through the following link:

We hope you like our presentation and enjoy the rest of the Holidays!

In reply to Paula Joy Aliposa

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Lydia LEONARDO -
Thank you for a very succinct but substantial report on the development of the cochlea. My questions are:
1. You mentioned the FGF and Notch pathway responsible for the number of sensory cells. Is the number of sensory cells specific or definite?
2. What chemical and mechanical factors can affect the hair cells in the cochlea? Are the hair and stereocilia incapable of regeneration?
Thank you.
In reply to Lydia LEONARDO

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Rogene Cezar Marie Bueno -

Good day, Ma'am!

Here are our responses to your questions.

1. Based on the studies conducted by Hayashi et al. (2008) and Dabdoub et al. (2008), the number of resulting sensory cells are neither specific nor definite. Instead, the number of the sensory cells is variable and dependent on how the prosensory cells maintained the expression of certain transcriptional factors (Sox2), and whether FGF signaling components are inhibited or deleted. Irregularities in could lead to severe reduction in the number of sensory cells in the cochlea.

2. The hair cells of the cochlea are responsible in hearing and balance. The vibrations from soundwaves shake the hairs attached which are then transferred to the cells and are transformed into electrical signals which are sent to the brain to be understood. The hair cells are also accompanied by the endolymph which is a special fluid with a higher charge potential from the rest of the body because of higher k+ ion concentration. Excessive vibrations can cause hair cells to be damaged while improper ion concentration can weaken the mechanotransduction of the cells which all result to hearing loss.

Although the stereocilia and hair cells of lower vertebrates, birds and other mammals can regenerate humans do not have this capability (John Hopkins Medicine, 2019). Only vestibular hair cells which focuses on providing balance can regenerate and any damaged cochlear hair cell is permanently destroyed which is why older people have trouble hearing. On the other hand, according to Yang, et al.(2012), expression of Atoh1 gene in damaged hair cells allows regeneration although the procedure needs to be performed within 10 days after the incident that caused hearing loss.

References:

Dabdoub, A., Puligilla, C., Jones, J. M., Fritzsch, B., Cheah, K. S. E., Pevny, L. H., & Kelley, M. W. (2008). Sox2 signaling in prosensory domain specification and subsequent hair cell differentiation in the developing cochlea. Proceedings of the National Academy of Sciences, 105(47), 18396–18401. doi:10.1073/pnas.0808175105

Hayashi, T., Ray, C. A., & Bermingham-McDonogh, O. (2008). Fgf20 is required for sensory epithelial specification in the developing cochlea. The Journal of neuroscience : the official journal of the Society for Neuroscience, 28(23), 5991–5999. https://doi.org/10.1523/JNEUROSCI.1690-08.2008

John Hopkins Medicine. (2019, July 9). Researchers find proteins that might restore damaged sound-detecting cells in the ear. ScienceDaily. Retrieved January 2, 2022, from https://www.sciencedaily.com/releases/2019/08/190805101127.htm

Yang, S. M., Chen, W., Guo, W. W., Jia, S., Sun, J. H., Liu, H. Z., Young, W. Y., & He, D. Z. Z. (2012). Regeneration of Stereocilia of Hair Cells by Forced Atoh1 Expression in the Adult Mammalian Cochlea. PLoS ONE, 7(9). https://doi.org/10.1371/journal.pone.0046355

Thank you and we hope you enjoyed the holidays!

 

In reply to Paula Joy Aliposa

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Janna Dominique Marasigan -
Greetings! First of all, I, along with my group mates (Morada and Cionelo), would like to commend your group (Acar, Aliposa, and Bueno) for your informative presentation. Next, I just want to ask, given the need to further decipher the molecular mechanisms that underlie the development of the inner ear, through what available approaches can this be achieved? Thank you so much, and Happy New Year to you all!
In reply to Janna Dominique Marasigan

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Paula Joy Aliposa -
Good Evening JD and Leomer!

Indeed there is still a need to further elucidate the molecular mechanisms involved in the development of the inner ear. To answer your question, there are actually different approaches to do this. There are inhibitory approaches to elucidate morphogenetic pathways (Sai et al., 2014), conditional approaches to test signaling pathways (Bok et al., 2013), as well as microarray, RNA-seq, and qPCR approaches for the elucidation of proteins and other signaling pathways involved in cochlear morphogenesis (Mann et al., 2014).

We hope this answers your question and happy new year to you both as well!

References:
Bok, J., Zenczak, C., Hwang, C.H. & Wu, D.K. (2013).
Auditory ganglion source of Sonic hedgehog regulates timing of cell cycle exit and differentiation of mammalian cochlear hair cells. Proc Natl Acad Sci USA, 110:13869-13874.
Mann, Z.F., Thiede, B.R., Chang, W., Shin, J.B., May-Simera, H.L., Lovett, M., Corwin, J.T. & Kelley, M.W. (2014). A gradient of Bmp7 specifies the tonotopic axis in the developing inner ear. Nature Communications, 5: 3839. https://doi.org/10.1038/ncomms4839
Sai, X., Yonemura, S. & Ladher, R.K. (2014). Junctionally restricted RhoA activity is necessary for apical constriction during phase 2 inner ear placode invagination. Developmental Biology, 394(2):206-216. https://doi.org/10.1016/j.ydbio.2014.08.022
In reply to Paula Joy Aliposa

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Fiona Ysabel Aurea Baradi -
Hi Cyrix, PJ and Rogene! Thank you for the short yet very informative report.

Our group (Baradi & Mores from LEC3) would like to ask if you could elaborate on the molecular mechanism or linkages (if there are any) between the PCP pathway and the formation of the polarized structure of hair bundles in the cochlea?

Thanks and happy new year! Stay safe.
In reply to Fiona Ysabel Aurea Baradi

Re: Bio 133 LEC3 [W 10 AM - 1 PM] FORMATION OF SENSORY ORGANS

by Paula Joy Aliposa -
Hello Fiona and Judge!

To summarize what Kelly and Chen (2009) indicated in the paper we discussed and to also answer your question, there are actually such linkages which have been identified. To be specific, these linkages revolve around the kinociliary genes and the kinocilium. Basically the hair bundles in the cochlea transiently contain kinocilia. And Jones et al. (2008) found that in the absence of kinociliary genes, the hair bundles become circular. However, it does not actually affect the asymmetric partitioning of core Planar Cell Polarity (PCP) proteins. Ultimately, this indicates that kinociliary genes downstream of the core PCP proteins play a role in providing direction for the formation of hair bundles
(2008).

We hope this short explanation elucidates more on this topic. Happy New Year to you guys as well!

References:
Jones, C., Roper, V.C., Foucher, I., Qian, D., Banizs,. B., Petit, C., Yoder, B.K., Chen, P. (2008). Ciliary proteins link basal body polarization to planar cell polarity regulation. Nature Genetics, 40: 69–77. https://doi.org/10.1038/ng.2007.54