Uranus on the MC in the birth charts of people often 'cause' news, shriek, people talking, changes at any level. For example: Karl Marx, Gerard Reve (Dutch homosexual author once on trial for blasphemy) and Dutch princess Margarita (who has Uranus square Ascendant, on top). She accused her aunt, the Queen, of actions against her ex-husband at the time.
Everything that happens and that is shocking (at any possible level or degree) has to do with Uranus. Transit Uranus conjunct the MC is most of the time repeating itself and signifies a hectic period in a changing life. The progressed MC conjunct Uranus is sometimes related to a the position of an outcast (liberating yourself from the past and the family destiny, voluntarily or not). And that, too, might not happen without tumultuous or even embarrassing events. Let me give some examples:
The progressed conjunction of Uranus and Midheaven in today’s chart of Prince Harry of England. He makes controversial and shocking remarks and has to do a training.
Transit Uranus opposition the Midheaven of Mata Hari when she was convicted to death, to her surprise and astonishment
Transit Uranus afflicting progressed Ascendant and Midheaven in Sarah Palin’s chart (starting the investigation of abuse of power)
Transit Uranus opposition Midheaven in the chart of Joe Biden (when his mother in law died and his son went to Iraq in the middle of election time)
Transit Uranus inconjunct Midheaven in Jesse Jackson’s chart (when he spoke of Obama’s balls)
The transit Midheaven quindecile Beenhakker’s Uranus when he lost the match Austria-Poland
More examples (about mice and Morales)