How I can Update only relevant data with this Update Controller?

Update Controller

exports.UpdatePanelMembers = (req, res) => {
  const { panelId } = req.params;
  if (panelId) {
    Panel.findOneAndUpdate(
      { _id: panelId },
      {
        panelMembers: {
          member1: {
            memberId: req.body.panelMembers.member1.memberId,
            fullName: req.body.panelMembers.member1.fullName,
            username: req.body.panelMembers.member1.username,
          },
          member2: {
            memberId: req.body.panelMembers.member2.memberId,
            fullName: req.body.panelMembers.member2.fullName,
            username: req.body.panelMembers.member2.username,
          },
          member3: {
            memberId: req.body.panelMembers.member3.memberId,
            fullName: req.body.panelMembers.member3.fullName,
            username: req.body.panelMembers.member3.username,
          },
        },
      }
    ).exec((error, result) => {
      if (error) return res.status(400).json({ error });
      if (result) {
        res.status(202).json({ result });
      }
    });
  }
};

In this code, if I update member1 details only, other data will be erased. So I want to update only relevant data like this postman JSON.

Postmen JSON Code

{
    "panelMembers": {
        "member1": {
            "username":"john.j",
            "fullName":"John Jade",
            "memberId":"member123"
        }
    }
}

Postmen ScreenShot