Drosha Isoforms in Stem Cells and Germ Line Mice
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Questions and Answers

What is the role of Drosha in miRNA biogenesis?

Drosha initiates the miRNA biogenesis process.

How does the newly identified Drosha isoform differ in expression compared to the canonical isoform?

The novel Drosha isoform is specifically expressed in embryonic stem cells and germ cells, differing from the canonical isoform.

What significance does the 5' UTR of the ESC/GC specific Drosha isoform hold?

The 5' UTR is different from the annotated isoform, which may influence its expression regulation.

Why is the study of cell-type specific isoforms of miRNA biogenesis factors important?

<p>They contribute to the accurate control of miRNA biogenesis essential for normal development.</p> Signup and view all the answers

What does the differential use of ATG codons suggest about the Drosha isoform in pluripotent cells?

<p>It indicates a conserved characteristic of the Drosha locus, favoring the second ATG in pluripotent cells.</p> Signup and view all the answers

What did the reanalysis of Ribo-seq data reveal about Drosha in human iPSCs?

<p>It showed no evidence of internal transcription initiation of Drosha in human iPSCs.</p> Signup and view all the answers

What developmental role has not been previously reported for Drosha?

<p>No previous studies have reported a developmental role for a cell-type specific isoform of Drosha.</p> Signup and view all the answers

What methodology was used to identify the novel TSS at the mouse Drosha locus?

<p>An integrative analysis of publicly available transcriptome data was used.</p> Signup and view all the answers

What implications might the presence of a specific Drosha isoform have on embryonic stem cell development?

<p>The presence of a specific Drosha isoform may allow for precise regulation of miRNA biogenesis essential for proper cell differentiation during embryonic development.</p> Signup and view all the answers

In what way does the novel Drosha isoform's start codon impact its protein translation?

<p>The novel Drosha isoform begins translation at the second methionine of the canonical isoform, potentially altering its functional properties.</p> Signup and view all the answers

How might RNA binding proteins affect the expression of the ESC/GC specific Drosha isoform?

<p>RNA binding proteins could mediate differential expression by interacting with the unique 5' UTR of the ESC/GC specific Drosha isoform.</p> Signup and view all the answers

What does the lack of documented internal transcription initiation of Drosha in human iPSCs suggest about species differences?

<p>It suggests that while the use of the second ATG codon is conserved in pluripotent cells, the mechanisms regulating isoform expression may differ between mammals.</p> Signup and view all the answers

What potential role does the identified novel TSS at the mouse Drosha locus play in ESCs and GCs?

<p>The novel TSS may enable the production of a Drosha isoform that is specifically tailored for the unique regulatory needs of ESCs and GCs.</p> Signup and view all the answers

Why might the differential use of ATG codons in HEK293T cells and iPSCs be significant?

<p>This differential use might indicate a specialized adaptation in translation initiation that impacts cellular functions and miRNA processing.</p> Signup and view all the answers

How does the study of the novel Drosha isoform contribute to our understanding of miRNA regulation in mammals?

<p>It enhances our knowledge of cell-type specific miRNA regulation and highlights the complexity of miRNA biogenesis machinery in mammalian development.</p> Signup and view all the answers

What relevance does the identification of an isoform specifically expressed in germ cells have for reproductive biology?

<p>This relevance lies in the potential impact on gametogenesis and the role of miRNAs in the development of gametes.</p> Signup and view all the answers

Study Notes

Novel Drosha Isoform in Embryonic Stem Cells

  • MicroRNAs (miRNAs) are approximately 22 nucleotide small non-coding RNAs essential for regulating target mRNAs and play a critical role in normal development.
  • Regulation of miRNA biogenesis factors like DGCR8, Dicer, and Ago2 is known to be influenced by cell-type specific isoforms, which is crucial for proper miRNA processing during mammalian development.
  • A novel internal transcription start site (TSS) was identified at the mouse Drosha locus, leading to a specific isoform expressed predominantly in embryonic stem cells (ESC) and germ cells (GC).

Differences in Isoform Expression

  • The 5' untranslated region (UTR) of the ESC/GC specific Drosha isoform differs from that of the canonical Drosha isoform.
  • This variation in the 5' UTR may allow for distinct regulatory mechanisms, potentially involving upstream Open Reading Frames (uORFs) and RNA binding proteins that modulate isoform expression.

Mechanism of Translation

  • The translation process for the ESC/GC specific Drosha isoform is expected to initiate at the second methionine codon of the canonical Drosha isoform, which may indicate a unique feature in pluripotent cells.

Comparative Analysis with Human Cells

  • Analysis revealed no internal transcription initiation of Drosha in human induced pluripotent stem cells (iPSCs).
  • Re-examination of Ribo-seq data suggested that HEK293T cells and iPSCs exhibit different usages of the initial ATG codons, with pluripotent cells favoring the second ATG. This implies a conserved mechanism of isoform expression across species, despite the differing approaches in mice and humans.

Novel Drosha Isoform in Embryonic Stem Cells

  • MicroRNAs (miRNAs) are approximately 22 nucleotide small non-coding RNAs essential for regulating target mRNAs and play a critical role in normal development.
  • Regulation of miRNA biogenesis factors like DGCR8, Dicer, and Ago2 is known to be influenced by cell-type specific isoforms, which is crucial for proper miRNA processing during mammalian development.
  • A novel internal transcription start site (TSS) was identified at the mouse Drosha locus, leading to a specific isoform expressed predominantly in embryonic stem cells (ESC) and germ cells (GC).

Differences in Isoform Expression

  • The 5' untranslated region (UTR) of the ESC/GC specific Drosha isoform differs from that of the canonical Drosha isoform.
  • This variation in the 5' UTR may allow for distinct regulatory mechanisms, potentially involving upstream Open Reading Frames (uORFs) and RNA binding proteins that modulate isoform expression.

Mechanism of Translation

  • The translation process for the ESC/GC specific Drosha isoform is expected to initiate at the second methionine codon of the canonical Drosha isoform, which may indicate a unique feature in pluripotent cells.

Comparative Analysis with Human Cells

  • Analysis revealed no internal transcription initiation of Drosha in human induced pluripotent stem cells (iPSCs).
  • Re-examination of Ribo-seq data suggested that HEK293T cells and iPSCs exhibit different usages of the initial ATG codons, with pluripotent cells favoring the second ATG. This implies a conserved mechanism of isoform expression across species, despite the differing approaches in mice and humans.

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This quiz explores the role of a novel Drosha isoform specifically expressed in embryonic stem cells and germ line cells in mice. It highlights the significance of microRNAs in regulating target mRNAs and their impact on normal development.

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