NO, you do not need to make a transgenic construct.  You do not need to do homologous recombination.   The type of point mutation you desire is perfect for the cas9/Crspr system.   Given that the L210 mutation is not embryonic lethal, you should be able to do this in mice using a guide RNA close to the L210 codon.  We use the x330 vector to clone insert specific guide RNA. This plasmid also expresses cas9 and when injected into a fertilized egg, similar to making a transgenic mouse, the gRNA and cas9 create a double stranded break near the guide sequence.  You also inject an oligonucleotide or a piece of DNA that has the desired point mutation.  This template is then used to repair  the break , thereby introducing your mutation into the genome.  Newborn mice are then screened for the mutation.  It helps if your mutation of the L210 also creates a new restriction enzyme site. 

Check out the papers from the Jaenisch lab on cas9 for more details.

To generate your transgenic mouse with your desired mutation, the best way is to restart your work from your transgenic construct if you have already generated your transgenic mouse. What you need to do is to generate the mutation(s) whatever you want in your construct using site-directed mutagenesis, sequencing to verify the desired mutation(s), and then re-do your transgeneic mouse. This sounds time wasting but is actually the quick way to get what you want. Site-directed mutagenesis nowadays is just a simple PCR reaction.

NO, you do not need to make a transgenic construct.  You do not need to do homologous recombination.   The type of point mutation you desire is perfect for the cas9/Crspr system.   Given that the L210 mutation is not embryonic lethal, you should be able to do this in mice using a guide RNA close to the L210 codon.  We use the x330 vector to clone insert specific guide RNA. This plasmid also expresses cas9 and when injected into a fertilized egg, similar to making a transgenic mouse, the gRNA and cas9 create a double stranded break near the guide sequence.  You also inject an oligonucleotide or a piece of DNA that has the desired point mutation.  This template is then used to repair  the break , thereby introducing your mutation into the genome.  Newborn mice are then screened for the mutation.  It helps if your mutation of the L210 also creates a new restriction enzyme site. 

Check out the papers from the Jaenisch lab on cas9 for more details.

Gregory Dressler where did you find that a L210 mutation is non lethal. Because i found it was lethal.

There are two possible options, first is the one mentioned by Gregory Dressler, second if  you have the construct already and only want to introduce a point mutation: use QuikChange from Stratagene, paste your sequence in the primer design program: StraStratagenehttp://www.genomics.agilent.com/primerDesignProgram.jsp?&_requestid=31786

indicate the bases you want to have mutated, order the oligos (high purity), do the PCR sequence and ready. I did some transgenic reporter lines this way.

Gregory Dressler  is right, follow the crispr cas9 way and you will see the wonders. this is so far the cheapest and most easiest way of generating targeted mutations. Just one improvement: use cas9 protein (NEB etc supplies it) and Sg RNA , mix it put it at 37 degrees for 15 min and than put it on ice and inject. you will get great results with less off targets and more survivability. Good luck

I was just guessing.  When you said dilated cardiomyopathy , I assumed that is a post-natal phenotype, i.e. it is not embryonic lethal which is important because the cas9 is so efficient that you will get many homozygote mutants even in the F0 generation.